Tibial implant and systems with variable slope

ABSTRACT

Methods and devices are disclosed relating improved articular models, implant components, and related guide tools and procedures. In addition, methods and devices are disclosed relating articular models, implant components, and/or related guide tools and procedures that include one or more features derived from patient-data, for example, images of the patient&#39;s joint. The data can be used to create a model for analyzing a patient&#39;s joint and to devise and evaluate a course of corrective action. The data also can be used to create patient-adapted implant components and related tools and procedures.

RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 12/660,529, filedFeb. 25, 2010, entitled “Patient-Adapted and Improved ArticularImplants, Designs and Related Guide Tools,” which claims the benefit of:U.S. Ser. No. 61/155,362, entitled “Patient-Specific Orthopedic ImplantsAnd Models,” filed Feb. 25, 2009; U.S. Ser. No. 61/269,405, entitled“Patient-Specific Orthopedic Implants And Models,” filed Jun. 24, 2009;U.S. Ser. No. 61/273,216, entitled “Patient-Specific Orthopedic ImplantsAnd Models,” filed Jul. 31, 2009; U.S. Ser. No. 61/275,174, entitled“Patient-Specific Orthopedic Implants And Models,” filed Aug. 26, 2009;U.S. Ser. No. 61/280,493, entitled “Patient-Adapted and ImprovedOrthopedic Implants, Designs and Related Tools,” filed Nov. 4, 2009;U.S. Ser. No. 61/284,458, entitled “Patient-Adapted And ImprovedOrthopedic Implants, Designs And Related Tools,” filed Dec. 18, 2009;U.S. Ser. No. 61/155,359, entitled “Patient Selectable JointArthroplasty Devices and Surgical Tools,” filed Feb. 25, 2009; and U.SSer. No. 61/220,726, entitled “Patient-Specific Orthopedic Implants AndModels,” filed Jun. 26, 2009.

U.S. Ser. No. 12/660,529 is also a continuation-in-part of US. Ser. No.12/712,072, entitled “Automated Systems For ManufacturingPatient-Specific Orthopedic Implants And Instrumentation” filed Feb. 24,2010, which claims the benefit of U.S. Ser. No. 61/208,440, entitled“Automated Systems for Manufacturing Patient-Specific OrthopedicImplants and Instrumentation” filed Feb. 24, 2009, and US. Ser. No.61/208,444, entitled “Automated Systems for ManufacturingPatient-Specific Orthopedic Implants and Instrumentation” filed Feb. 24,2009.

Each of the above-described applications is hereby incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The invention relates to improved and/or patient-adapted (e.g.,patient-specific and/or patient-engineered) orthopedic implants andguide tools, as well as related methods, designs and models.

BACKGROUND

Generally, a diseased, injured or defective joint, such as, for example,a joint exhibiting osteoarthritis, has been repaired using standardoff-the-shelf implants and other surgical devices. Specificoff-the-shelf implant designs have been altered over the years toaddress particular issues. For example, several existing designs includeimplant components having rotating parts to enhance joint motion. Rieset al. describes design changes to the distal or posterior condyles of afemoral implant component to enhance axial rotation of the implantcomponent during flexion. See U.S. Pat. Nos. 5,549,688 and 5,824,105.Andriacchi et al. describes a design change to the heights of theposterior condyles to enhance high flexion motion. See U.S. Pat. No.6,770,099. However, in altering a design to address a particular issue,historical design changes frequently have created one or more additionalissues for future designs to address. Collectively, many of these issueshave arisen from one or more differences between a patient's existing orhealthy joint anatomy and the corresponding features of an implantcomponent.

Historically, joint implants have employed a one-size-fits-all (or afew-sizes-fit-all) approach to implant design that has resulted insignificant differences between a patient's existing or healthybiological structures and the resulting implant component features inthe patient's joint. Accordingly, advanced implant designs and relateddevices and methods that address the needs of individual patient's areneeded.

SUMMARY

The embodiments described herein include advancements in or arise out ofthe area of patient-adapted articular implants that are tailored toaddress the needs of individual, single patients. Such patient-adaptedarticular implants offer advantages over the traditionalone-size-fits-all approach, or a few-sizes-fit-all approach. Theadvantages include, for example, better fit, more natural movement ofthe joint, reduction in the amount of bone removed during surgery and aless invasive procedure. Such patient-adapted articular implants can becreated from images of the patient's joint. Based on the images,patient-adapted implant components can be selected and/or designed toinclude features (e.g., surface contours, curvatures, widths, lengths,thicknesses, and other features) that match existing features in thesingle, individual patient's joint as well as features that approximatean ideal and/or healthy feature that may not exist in the patient priorto a procedure. Moreover, by altering the design approach to addressseveral design implant issues, several non-traditional design approacheshave been identified that offer improvements over traditional implantdesigns.

Patient-adapted features can include patient-specific and/orpatient-engineered. Patient-specific (or patient-matched) implantcomponent or guide tool features can include features adapted to matchone or more of the patient's biological features, for example, one ormore biological/anatomical structures, alignments, kinematics, and/orsoft tissue impingements. Patient-engineered (or patient-derived)features of an implant component can be designed and/or manufactured(e.g., preoperatively designed and manufactured) based onpatient-specific data to substantially enhance or improve one or more ofthe patient's anatomical and/or biological features.

The patient-adapted (e.g., patient-specific and/or patient-engineered)implant components and guide tools described herein can be selected(e.g., from a library), designed (e.g., preoperatively designedincluding, optionally, manufacturing the components or tools), and/orselected and designed (e.g., by selecting a blank component or toolhaving certain blank features and then altering the blank features to bepatient-adapted). Moreover, related methods, such as designs andstrategies for resectioning a patient's biological structure also can beselected and/or designed. For example, an implant component bone-facingsurface and a resectioning strategy for the corresponding bone-facingsurface can be selected and/or designed together so that an implantcomponent's bone-facing surface matches the resected surface. Inaddition, one or more guide tools optionally can be selected and/ordesigned to facilitate the resection cuts that are predetermined inaccordance with resectioning strategy and implant component selectionand/or design.

In certain embodiments, patient-adapted features of an implantcomponent, guide tool or related method can be achieved by analyzingimaging test data and selecting and/or designing (e.g., preoperativelyselecting from a library and/or designing) an implant component, a guidetool, and/or a procedure having a feature that is matched and/oroptimized for the particular patient's biology. The imaging test datacan include data from the patient's joint, for example, data generatedfrom an image of the joint such as x-ray imaging, cone beam CT, digitaltomosynthesis, and ultrasound, a MRI or CT scan or a PET or SPECT scan,is processed to generate a varied or corrected version of the joint orof portions of the joint or of surfaces within the joint. Certainembodiments provide method and devices to create a desired model of ajoint or of portions or surfaces of a joint based on data derived fromthe existing joint. For example, the data can also be used to create amodel that can be used to analyze the patient's joint and to devise andevaluate a course of corrective action. The data and/or model also canbe used to design an implant component having one or morepatient-specific features, such as a surface or curvature.

In one aspect, embodiments described herein provide a pre-primaryarticular implant component that includes (a) an outer, joint-facingsurface and an inner, bone-facing surface. The outer, joint-facingsurface can include a bearing surface. The inner joint facing surfacecan include one or more patient-engineered bone cuts selected and/ordesigned from patient-specific data. In certain embodiments, thepatient-engineered bone cuts can be selected and/or designed frompatient-specific data to minimize the amount of bone resected in one ormore corresponding predetermined resection cuts. In certain embodiments,the patient-engineered bone cuts substantially negatively-match one ormore predetermined resection cuts. The predetermined resection cuts canbe made at a first depth that allows, in a subsequent procedure, removalof additional bone to a second depth required for a traditional primaryimplant component. In addition, the pre-primary articular implantcomponent can be a knee joint implant component, a hip joint implantcomponent, a shoulder joint implant component, or a spinal implantcomponent. For example, the pre-primary articular implant component canbe a knee joint implant component, such as a femoral implant component.Moreover, the pre-primary articular implant component can include six ormore (e.g., six, seven, eight, nine, ten, eleven, twelve, thirteen, ormore) patient-engineered bone cuts on its bone facing surface.

In certain embodiments, the pre-primary articular implant component caninclude an implant component thickness in one or more regions that isselected and/or designed from patient-specific data to minimize theamount of bone resected. The one or more regions comprises the implantcomponent thickness perpendicular to a planar bone cut and between theplanar bone cut and the joint-surface of the implant component.

In another aspect, embodiments described herein provide methods forminimizing resected bone from, and/or methods for making an articularimplant for, a single patient in need of an articular implantreplacement procedure. These methods can include (a) identifyingunwanted tissue from one or more images of the patient's joint; (b)identifying a combination of resection cuts and implant componentfeatures that remove the unwanted tissue and also provide maximum bonepreservation; and (c) selecting and/or designing for the patient acombination of resection cuts and implant component features thatprovide removal of the unwanted tissue and maximum bone preservation. Incertain embodiments, the unwanted tissue is diseased tissue or deformedtissue.

In certain embodiments, step (c) can include designing for the singlepatient a combination of resection cuts and implant component featuresthat provide removal of the unwanted tissue and maximum bonepreservation. Designing can include manufacturing. Moreover, the implantcomponent features in step (c) can include one or more of the featuresselected from the group consisting of implant thickness, bone cutnumber, bone cut angles, and/or bone cut orientations.

In certain embodiments, a measure of bone preservation can include totalvolume of bone resected, volume of bone resected from one or moreresection cuts, volume of bone resected to fit one or more implantcomponent bone cuts, average thickness of bone resected, averagethickness of bone resected from one or more resection cuts, averagethickness of bone resected to fit one or more implant component bonecuts, maximum thickness of bone resected, maximum thickness of boneresected from one or more resection cuts, maximum thickness of boneresected to fit one or more implant component bone cuts.

In certain embodiments, a minimum implant component also can beestablished. For example, step (a) also can include identifying aminimum implant component thickness for the single patient. Step (b)also can include identifying a combination of resection cuts and/orimplant component features that provide a minimum implant thicknessdetermined for the single patient. Step (c) also can include selectingand/or designing the combination of resection cuts and/or implantcomponent features that provides at least a minimum implant thicknessfor the single patient. The minimum implant component thickness is basedon one or more of femur and/or condyle size or patient weight.

The articular implant component can be a knee joint implant component, ahip joint implant component, a shoulder joint implant component, or aspinal implant component. For example, the pre-primary articular implantcomponent can be a knee joint implant component, such as a femoralimplant component.

In another aspect, embodiments described herein provide a femoralimplant component that includes (a) a joint-facing surface comprising abearing surface portion, and (b) a bone-facing surface comprising six ormore bone cuts.

In another aspect, embodiments described herein provide a femoralimplant component that includes (a) a joint-facing surface comprising abearing surface portion, and (b) a bone-facing surface comprising adistal bone cut having two or more planar facets or portions that arenon-coplanar with each other. In certain embodiments, the two or morefacets or portions are non-parallel with each other. The first of thetwo or more facets or portions can be on a lateral condyle bone-facingsurface and the second can be on a medial condyle bone-facing surface.

In another aspect, embodiments described herein provide a femoralimplant component that includes (a) a joint-facing surface comprising abearing surface portion, and (b) a bone-facing surface comprising ananterior bone cut having two or more planar facets or portions that arenon-coplanar with each other. In certain embodiments, the two or moreplanar facets or portions are non-parallel with each other.

In another aspect, embodiments described herein provide a femoralimplant component that includes (a) a joint-facing surface comprising abearing surface portion, and (b) a bone-facing surface comprising aposterior bone cut having two or more facets or portions that arenon-parallel with each other. In certain embodiments, the first of thetwo or more facets or portions can be on a lateral condyle bone-facingsurface and the second can be on a medial condyle bone-facing surface.

In another aspect, embodiments described herein provide a femoralimplant component that includes (a) a joint-facing surface comprising abearing surface portion, and (b) a bone-facing surface comprising ananterior chamfer bone cut having two or more planar facets or portionsthat are non-coplanar with each other. In certain embodiments, the twoor more planar facets or portions are non-parallel with each other. Thefirst of the two or more facets or portions can be on a lateral condylebone-facing surface and the second can be on a medial condylebone-facing surface.

In another aspect, embodiments described herein provide a femoralimplant component that includes (a) a joint-facing surface comprising abearing surface portion, and (b) a bone-facing surface comprising aposterior chamfer bone cut having two or more facets or portions thatare non-parallel with each other. In certain embodiments, the first ofthe two or more facets or portions can be on a lateral condylebone-facing surface and the second can be on a medial condylebone-facing surface.

In another aspect, embodiments described herein provide a femoralimplant component that includes (a) a joint-facing surface comprisinglateral and medial condylar surface portions, and (b) a bone-facingsurface comprising an anterior bone cut, wherein the distance betweenthe anterior bone cut and the lateral condylar surface portion isdifferent from the distance between the anterior bone cut and the medialcondylar surface portion. In certain embodiments, the two or more facetsor portions are substantially non-parallel.

In another aspect, embodiments described herein provide a femoralimplant component that includes (a) a lateral and medial condylarportions, and (b) a bone-facing surface comprising a distal bone cutfacet that is asymmetric about its center line in a sagittal plane. Incertain embodiments, the asymmetric distal bone cut facet lies on thebone-facing surface of the lateral condyle. In certain embodiments, thefemoral implant component of claim 38, wherein the asymmetric distalbone cut facet lies on the bone-facing surface of the medial condyle.

In another aspect, embodiments described herein provide a femoralimplant component that includes a femoral implant component having abone-facing surface comprising one or more bone cuts, wherein at leastone of the one or more bone cuts comprises two planar bone cut facetsseparated by at least one step cut. In certain embodiments, the step cutis substantially perpendicular to at least one of the bone cut facets.In certain embodiments, the step cut can rise or fall at about 30degrees or more from at least one of the bone cut facet planes.

In another aspect, embodiments described herein provide implantcomponents having an inner, bone-facing surface designed tonegatively-match a bone surface that was cut, for example based onpre-determined geometries or based on patient-specific geometries. Incertain embodiments, an outer joint-facing surface includes at least ina portion that substantially negatively-matches a feature of thepatient's anatomy and/or an opposing outer joint-facing surface of asecond implant component. In certain embodiments, by creatingnegatively-matching component surfaces at a joint interface, theopposing surfaces may not have an anatomic or near-anatomic shape, butinstead may be negatively-matching or near-negatively-matching to eachother. This can have various advantages, such as reducing implant andjoint wear and providing more predictable joint movement.

In another aspect, some embodiments provide implant components havingone or more patient-specific curvatures or radii of curvature in onedimension, and one or more standard or engineered curvatures or radii ofcurvature in a second dimension.

In another aspect, some embodiments provide methods of designing,selecting, manufacturing, and implanting the patient-adapted implantcomponents.

It is to be understood that the features of the various embodimentsdescribed herein are not mutually exclusive and may exist in variouscombinations and permutations.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects, features, and advantages ofembodiments will become more apparent and may be better understood byreferring to the following description, taken in conjunction with theaccompanying drawings, in which:

FIGS. 1A and 1B show schematic representations in a coronal plane of apatient's distal femur (FIG. 1A) and a femoral implant component (FIG.1B);

FIG. 2 is a flow chart illustrating a process that includes selectingand/or designing an initial patient-adapted implant;

FIG. 3 is a flow chart illustrating a process that includes selectingand/or designing a second patient-adapted implant;

FIGS. 4A-4M illustrate exemplary traditional implants includingtraditional knee joint implants (FIGS. 4A and 4B), traditional hip-jointimplants (FIGS. 4C-4G), traditional shoulder-joint implants (FIGS.4H-4J), and traditional spinal implants (FIGS. 4K-4M);

FIGS. 5A-5C schematically represent three illustrative embodiments ofimplants and/or implant components;

FIGS. 6A-6C depict designs of implant components that have six bone cuts(FIG. 6A), seven bone cuts (FIG. 6B), and three bone cuts with one beinga curvilinear bone cut (FIG. 6C);

FIG. 7A is a photograph showing an exemplary knee replacement using apatient-specific bicompartmental device and a patient-specificunicompartmental device;

FIGS. 7B and 7C are x-ray images showing the device of FIG. 7A in thecoronal plane and in the sagittal plane, respectively;

FIGS. 8A-8E show an exemplary design of a two-piece implant component;

FIG. 9 is a flow chart illustrating a process for generating a model ofa patient's joint (and/or a resection cut, guide tool, and/or implantcomponent);

FIG. 10A is a drawing of a cross-sectional view of an end of a femurwith an osteophyte; FIG. 10B is a drawing of the end of the femur ofFIG. 10A with the osteophyte virtually removed; FIG. 10C is a drawing ofthe end of the femur of FIG. 10B with the osteophyte virtually removedand showing a cross-sectional view of an implant designed to the shapeof the femur with the osteophyte removed; FIG. 10D is a drawing of theend of the femur of FIG. 10A and shows a cross-sectional view of animplant designed to the shape of the femur with the osteophyte intact;

FIG. 11A is a drawing of a cross-sectional view of an end of a femurwith a subchondral void in the bone; FIG. 11B is a drawing of the end ofthe femur of FIG. 11A with the void virtually removed; FIG. 11C is adrawing of the end of the femur of FIG. 11B with the void virtuallyremoved and showing a cross-sectional view of an implant designed to theshape of the femur with the void removed; FIG. 11D is a drawing of theend of the femur of FIG. 11A and showing a cross-sectional view of animplant designed to the shape of the femur with the void intact;

FIGS. 12A and 12B illustrate models for one particular patient receivinga single compartment knee implant and in need of osteophyte removalprior to placement of the implant components;

FIGS. 13A and 13B illustrate models for one particular patient receivinga bicompartmental knee implant and in need of osteophyte removal priorto placement of the implant components;

FIG. 14 displays an image of user interface for a computer softwareprogram for generating models of patient-specific renderings of implantassembly and defects (e.g., osteophyte structures), together with bonemodels;

FIG. 15 shows an illustrative flow chart of the high level processes ofan exemplary computer software program for generating models ofpatient-specific renderings of implant assembly and defects (e.g.,osteophyte structures), together with bone models;

FIG. 16 illustrates a coronal plane of the knee with exemplary resectioncuts that can be used to correct lower limb alignment in a kneereplacement;

FIG. 17 depicts a coronal plane of the knee shown with femoral implantmedial and lateral condyles having different thicknesses to help tocorrect limb alignment;

FIG. 18 illustrates a virtual model of a patient's limb that ismisaligned in the sagittal plane, for example, a genu antecurvatumdeformity, and the virtually corrected limb;

FIG. 19A illustrates perimeters and areas of two bone surface areas fortwo different bone resection cut depths; FIG. 19B is a distal view ofthe femur in which two different resection cuts are applied;

FIG. 20 depicts a femoral implant component having six bone cuts withthe intersect of bone cuts on the inner, bone-facing surface of theimplant highlighted;

FIG. 21 illustrates a computer model of a distal femur having optimizedbone cuts for a pre-primary implant overlaid with a traditional primaryimplant (shown in outline);

FIGS. 22A and 22B depict the posterior margin of an implant componentselected and/or designed using the imaging data or shapes derived fromthe imaging data so that the implant component will not interfere withand stay clear of the patient's PCL;

FIGS. 23A and 23B schematically show a traditional implant componentthat dislocates the joint-line; FIG. 23C schematically shows apatient-specific implant component in which the existing or naturaljoint-line is retained;

FIG. 24 depicts an implant or implant design that includes a straightdistal cut, a straight anterior cut, a straight posterior cut, andcurvilinear chamfer cuts;

FIGS. 25A and 25B schematically show a patient-specific implantcomponent designed to substantially positively-match the patient'sexisting or natural joint gap;

FIG. 26 is a flow chart illustrating the process of assessing andselecting and/or designing one or more implant component features and/orfeature measurements, and, optionally assessing and selecting and/ordesigning one or more resection cut features and feature measurements,for a particular patient;

FIG. 27 is an illustrative flow chart showing exemplary steps taken by apractitioner in assessing a joint and selecting and/or designing asuitable replacement implant component;

FIGS. 28A through 28K show implant components with exemplary featuresthat can be selected and/or designed, e.g., derived frompatient-specific and adapted to a particular patient, as well as beincluded in a library;

FIG. 29 shows a coronal view of a patient's femoral bone and, in dashedlines, standard bone cuts performed with a traditional total kneeimplant;

FIGS. 30A and 30B show the surface area of all or part of thebone-facing surface of the implant component substantially matching thecorresponding resected surface area of a patient's femur;

FIG. 31A shows a femoral implant component with the thinnest part of theimplant component appearing at the intersection of the implantcomponent's distal bone cut and a posterior chamfer bone cut; FIG. 31Billustrates an FEA analysis of the same implant component;

FIGS. 32A and 32B show the load bearing surfaces of a femoral implantcomponent in a coronal view (FIG. 32A) and in a sagittal view (FIG.32B);

FIGS. 33A through 33F illustrate exemplary types of curvatures for oneor more condylar coronal or sagittal curvatures;

FIGS. 34A and 34B illustrate a design for a femoral implant componenthaving a J-curve that is patient-specific in part and patient-engineeredin part.

FIGS. 35A and 35B illustrate two femoral implant components, one havinga J-curve that is substantially patient-specific and one having aJ-curve that is partially patient-specific and partiallypatient-engineered;

FIG. 36 illustrates the use of a coronal curvature having a longerradius of curvature versus a coronal curvature having shorter radius ofcurvature;

FIGS. 37A and 37B show cross-sections from a coronal view of two femoralcondyle sections of a femoral component;

FIG. 38 illustrates a patient's J-curve can be determined independentlyfor lateral and medial condyles;

FIG. 39 illustrates a trochlear J-curve on a model of a femur;

FIG. 40 illustrates a sulcus line of a femoral implant component;

FIG. 41A depicts an axial view of a particular patient's femoral shape;FIGS. 41B through 41V depict overlays of an implant component'sarticulating surface over the particular patient's femoral shape inaxial (FIGS. 41B-41N) and sagittal (FIG. 41O-41V) views;

FIG. 42A through 42C illustrate femoral implant components includes fivebone cuts, six bone cuts, and six flexed bone cuts, respectively;

FIGS. 43A through 43F show exemplary cross-sections of femoral implantcomponents with bone cuts shown as dashed lines;

FIGS. 44A-44C illustrate a femoral implant component having six bonescuts that include one or more parallel and non-coplanar facets;

FIGS. 45A-45B illustrate a femoral implant component having seven bonescuts that include one or more parallel and non-coplanar facets;

FIG. 46 illustrates a resection cut facet separated from one or morecorresponding facets by an intercondylar space and/or by a step cut;

FIGS. 47A and 47B are schematic views of a femur and patella andexemplary resection cut planes;

FIG. 48 is a schematic view of a sagittal plane of a femur with facetcuts indicated;

FIGS. 49A and 49B illustrate a femoral implant component comprising anintercondylar housing (sometimes referred to as a “box”);

FIGS. 50A and 50B illustrate a femoral implant component comprising andintercondylar box (FIG. 50A) or intercondylar bars (FIG. 50B) and anengaging tibial implant component;

FIG. 51 illustrates a femoral implant component comprising modularintercondylar bars or a modular intercondylar box;

FIGS. 52A through 52K show various embodiments and aspects ofcruciate-sacrificing femoral implant components and FIGS. 52L through52P show lateral views of different internal surfaces of intercondylarboxes;

FIG. 53A illustrates a variety of peg configurations that can be usedfor the implant components described herein; FIG. 53B illustrates anembodiments of a peg having a cross-section that includes a “+” orcross-like configuration;

FIGS. 54A and 54B show bone cement pockets in an embodiment of animplant component (FIG. 54A) and in a traditional component (FIG. 54B);

FIGS. 55A through 55F illustrate a preferred embodiment of the femoralimplant component and resection cuts;

FIGS. 56A to 56C illustrates how a patellar resection depth alters theresultant patellar resection profile;

FIG. 57 illustrates a prolate-shaped patella implant component;

FIGS. 58A-58D show various aspects of embodiments of patella implantcomponents;

FIGS. 59A and 59B show flow charts of exemplary processes for optimizingselecting and/or designing, and optionally optimizing, a patellarcomponent based on one or more patient-specific biological features;

FIGS. 60A and 60B show exemplary unicompartmental medial and lateraltibial implant components without (FIG. 60A) and with (FIG. 60B) apolyethylene layer or insert;

FIGS. 61A to 61C depict three different types of step cuts separatingmedial and lateral resection cut facets on a patient's proximal tibia;

FIGS. 62A and 62B show exemplary flow charts for deriving a medialtibial component slope (FIG. 62A) and/or a lateral tibial componentslope (FIG. 62B) for a tibial implant component;

FIGS. 63A through 63J show exemplary combinations of tibial traydesigns;

FIGS. 64A through 64F include additional embodiments of tibial implantcomponents that are cruciate retaining;

FIG. 65 shows proximal tibial resection cut depths of 2 mm, 3 mm and 4mm;

FIG. 66 shows exemplary small, medium and large blank tibial trays;

FIG. 67 shows exemplary A-P and peg angles for tibial trays;

FIG. 68A shows six exemplary tool tips a polyethylene insert for atibial implant component; FIG. 68B shows a sagittal view of twoexemplary tools sweeping from different distances into the polyethyleneinsert;

FIG. 69A shows an embodiment in which the shape of the concave groove onthe medial side of the joint-facing surface of the tibial insert ismatched by a convex shape on the opposing surface of the insert and by aconcavity on the engaging surface of the tibial tray;

FIG. 69B illustrates two exemplary concavity dimensions for the bearingsurface of a tibial implant component;

FIG. 70 illustrates two embodiments of tibial implant components havingslopped sagittal J-curves;

FIGS. 71A and 71B depict exemplary cross-sections of tibial implantcomponents having a post (or keel or projection) projecting from thebone-facing surface of the implant component;

FIG. 72A is a flow chart for adapting a blank implant component for aparticular patient; FIG. 72B illustrates various tibial cuts andcorresponding surface features;

FIG. 73A depicts a medial balancer chip insert from top view to show thesuperior surface of the chip; FIG. 73B depicts a side view of a set offour medial balancer chip inserts; FIG. 73C depicts a medial balancingchip being inserted in flexion between the femur and tibia; FIG. 73Ddepicts the medial balancing chip insert in place while the knee isbrought into extension; FIG. 73E depicts a cutting guide attached to themedial balancing chip; FIG. 73F shows that the inferior surface of themedial balancing chip can act as cutting guide surface for resectioningthe medial portion of the tibia;

FIG. 74A depicts a set of three medial spacer block inserts havingincrementally increasing thicknesses; FIG. 74B depicts a set of twomedial femoral trials having incrementally increasing thicknesses; FIG.74C depicts a medial femoral trial in place and a spacer block beinginserted to evaluate the balance of the knee in flexion and extension;

FIG. 75A depicts a set of three medial tibial component insert trialshaving incrementally increasing thicknesses; FIG. 75B depicts theprocess of placing and adding various tibial component insert trials;FIG. 75C depicts the process of placing the selected tibial componentinsert;

FIG. 76 illustrates a guide tool having one or more apertures forestablishing resected holes in a patient's biological structure;

FIG. 77 illustrates a guide tool having a moveable aperture and bushing;

FIG. 78 shows a guide tool for making distal and posterior resectioncuts to the distal femur;

FIGS. 79A and 79B show two options for a third guide tool for makinganterior and posterior chamfer cuts;

FIG. 80 illustrates a single, “all-in-one” guide tool that can be usedto establish all the resection cuts associated with installation of afemoral implant component;

FIGS. 81A and 81B illustrate optional guide tool attachments that can beused to enhance one or more cutting or drilling surfaces;

FIG. 82A illustrates an embodiment of a single guide tool that can beused to establish the peg holes and all the resection cuts associatedwith installation of a femoral implant component; FIGS. 82B and 82Cillustrate three optional guide tool attachments for enhancing thecutting or drilling surfaces of the single guide tool;

FIG. 82D illustrates a set of resection cut guide tools that togethercan be used to facilitate peg holes and resection cuts for a patient'sfemur;

FIGS. 82E to 82H show another embodiment of a single guide tool andattachments that can be used to establish the peg holes and all theresection cuts associated with installation of a femoral implantcomponent;

FIGS. 83A to 83F illustrate a tibial guide tool, a tibial guide rod, anda tibial +2 mm additional resection cut guide; FIGS. 83G and 83Hillustrate one or more additional guide tools that can be included andused to remove additional bone from the proximal surface of the tibia;

FIG. 84A shows a tibial guide tool for making a resection cut; FIG. 84B,shows a tibial guide tool to resect into the resected tibial surface tocreate a notch for accepting the keel of a tibial implant component;

FIGS. 85A through 85D show exemplary tools for intraoperativelypreparing a rotated tibial implant component;

FIGS. 86A through 86D show the same front view of the guide tools andinserts shown in FIGS. 85A through 85D and, in addition, show front andback view of three exemplary inserts;

FIG. 87 is a flow chart illustrating an exemplary process for selectingand/or designing a patient-adapted total knee implant;

FIG. 88A illustrates a distal femur and a distal resection planeparallel to the epicondylar axis; FIG. 88B shows an example of ananterior oblique resection plane 8830.

FIGS. 89A to 89E show optimized resection cut planes to a patient'sfemur based on the medial condyle.

FIGS. 90A and 90B show resection cut planes for a patient's lateralcondyle posterior chamfer (FIG. 90A) and lateral condyle posterior (FIG.90B) cut planes that are independently optimized based onpatient-specific data for the lateral condyle;

FIGS. 91A and 91B illustrate two exemplary distal resection cut planesfor two different cut designs;

FIGS. 92A and 92B illustrate five femoral resection cuts for the twodesigns shown in FIGS. 91A and 91B, respectively;

FIGS. 93A and 93B illustrate the completed cut femur models for each oftwo cut designs;

FIG. 94A illustrates an embodiment of a cut plane design having anteriorand posterior cut planes that diverge from the component peg axis; FIG.94B illustrates an implant component design that includes a peg diameterof 7 mm with a rounded tip;

FIGS. 95A and 95B illustrate exemplary bone-facing surfaces of femoralimplant component designs that include a patient-adapted peripheralmargin;

FIGS. 96A and 96B illustrate side views of exemplary femoral implantcomponent designs;

FIG. 97 illustrates a femoral implant component (PCL-retaining) havingseven bone cuts;

FIG. 98A and FIG. 98B illustrate the resection cut planes for theimplant component of FIG. 97;

FIG. 99 illustrates the implant component of FIG. 97 from a differentangle to show cement pocket and peg features;

FIG. 100A shows a five-cut-plane femoral resection design for a femoralimplant component having five bone cuts; FIG. 100B shows aseven-cut-plane femoral resection design for a femoral implant componenthaving seven bone cuts;

FIG. 101A shows a patient's femur having five, not flexed resectioncuts; FIG. 101B shows the same femur but with five, flexed resectioncuts;

FIGS. 102A to 102D show outlines of a traditional five-cut femoralcomponent (in hatched lines) overlaid with, in 102A, a femur havingseven optimized resection cuts for matching an optimized seven-bone-cutimplant component; in FIG. 102B, a femur having five optimized resectioncuts for matching to an optimized five-bone-cut implant component; inFIG. 102C, a femur having five, not flexed resection cuts for matchingto an optimized five-bone-cut implant component; and in FIG. 102D, afemur having five, flexed resection cuts for matching to an optimizedfive-bone-cut, flexed implant component;

FIGS. 103A to 103F illustrate patient-adapted femoral implants andresection cuts for each of the three patients.

FIGS. 104A and 104B illustrate all-in-one femoral resection guide toolsfor each of two patients;

FIG. 105 illustrates a drill guide attachment for attaching to theall-in-one guide tool;

FIGS. 106A, 106B, and 106C show various too attachments for theall-in-one guide tool to extend one or more cutting surfaces;

FIGS. 107A, 107B, and 107C illustrate a set of three guide tools, whichcollectively supplied all of the guide slots and holes to perform eachof several predetermined femoral resection cuts and peg hole placements;

FIGS. 108A through 108F illustrate a different set of femoral guidetools to perform each of several predetermined femoral resection cutsand peg hole placements;

FIGS. 109A and 109B illustrate an anterior profile guide tool forassessing the peak profile at the anterior portion of the femur in theinstalled implant as compared to the patient's native knee;

FIG. 110A illustrates a cutting guide tool for accurately resectioningthe proximal tibia; FIG. 110B illustrates an alternate tibial cuttingguide tool; FIG. 110C illustrates a tibial alignment guide tool and downrod for confirming prior the alignment of the cutting guide tool; FIG.110D illustrates a resected tibia marked with a pen or other instrumentto establish landmarks for placement of subsequent tools;

FIG. 111A illustrates a tibial keel prep guide tool; FIG. 111Billustrates a set of tibial keel prep insert guides;

FIG. 112 illustrates a tibial keel prep guide tool for establishing thekeel slot in the patient's resected proximal tibial surface;

FIGS. 113A and 113B illustrates an alternative tibial keel prep guidetool;

FIG. 114A illustrates a set of tibial trial spacers; FIG. 114Billustrates a set of tibial implant component trial inserts;

FIGS. 115A and 115B illustrate a tibial implant component comprising atibial tray (FIG. 115A) and a set of tibial inserts (FIG. 115B);

FIG. 116A illustrates a set of patella sizers; FIG. 116B illustrates apatellar cutting tool to cut the patella to a predetermined depth ofresection; FIG. 116C illustrates implant trials; FIG. 116D illustrates apatellar implant;

FIGS. 117A through 117D show exemplary steps in a surgical implantationprocedure;

FIGS. 118A and 118B illustrate a patient-specific femoral model andposterior and anterior resection cut lines for a patient-specificimplant component having a curvilinear cut;

FIG. 119A to FIG. 119C illustrate steps for performing a curvilinearresection cut between planar anterior and posterior cuts on a medialcondyle;

FIGS. 120A to 120C illustrate steps for performing a curvilinearresection cut between planar anterior and posterior cuts on a lateralcondyle;

FIG. 121A illustrate a model of a femur having predetermined resectioncuts including a curvilinear cut; FIGS. 121B and 121C illustrate thecorresponding patient-specific implant component for the resection cutsdepicted in FIG. 121A;

FIG. 122A shows a model of a bone along with a jig that allowspreparation of predetermined resection holes and, optionally, resectioncuts surfaces to match predetermined resection cuts specific to apatient's particular anatomy; FIGS. 122B and 122C show an alternativeset of jigs that can be used with a router-type saw;

FIG. 123A shows a model of the prepared bone following jig-guided bonecuts; FIG. 123B shows the model of FIG. 123A with a two-piecepatient-specific implant component designed with an inner bone-facingsurface that substantially negatively-matches the patient's resectedbone surface, including curvilinear bone and resection cuts;

FIGS. 124A and 124B illustrate a femoral implant component designed withtwo pieces with one piece having on its inner, bone-facing surface asingle, posterior cut;

FIGS. 125A and 125B illustrate a femoral implant component design havingtwo pieces; FIG. 125C shows an example of the two-piece implantcomponent positioned on a model of the femur;

This example illustrates exemplary implant components having enhancedarticular surfaces (i.e., joint-facing surfaces). FIG. 126A is a frontschematic view of engaging portions of a single compartment (e.g., asingle condyle) of a knee implant; FIG. 126B is a cross-sectionalschematic view in the coronal plane of the femoral component of FIG.126A; FIGS. 126C to 126F show cross-sectional schematic views in thecoronal plane of respective alternate embodiments of the femoralcomponent;

FIGS. 127A to 127F illustrate an exemplary design of a knee implant,including a femoral component and a patella component;

FIG. 128 illustrates the mechanical axis of a patient's lower extremitydefined by the center of hip, the center of the knee, and the center ofthe ankle;

FIGS. 129A to 129C each illustrate a model showing the existingmisalignment of a patient's lower extremity and the virtual alignmentdetermined using the model;

FIGS. 130A to 130D illustrate virtual alignment steps relating todetermining a patient's tibial mechanical axis;

FIGS. 131A to 131F illustrate virtual alignment steps relating todetermining the coronal and sagittal planes of a patient's tibialmechanical axis;

FIGS. 132A to 132D illustrate virtual alignment steps relating todetermining a patient's femoral mechanical axis;

FIGS. 133A to 133D illustrate virtual alignment steps relating todetermining the coronal and sagittal planes of a patient's femoralmechanical axis;

FIGS. 134A and 134B illustrate virtual alignment steps for aligning apatient's femoral and tibial mechanical axes in coronal and sagittalplanes;

FIGS. 135A to 135G illustrate comparisons between the patient's beforeand after virtual alignment;

FIGS. 136A to 136C illustrate three femoral implant components that wereanalyzed by FEA, including, respectively, a component with six bone cutsand a perpendicular distal bone cut (“Perp 6-Cuts”), a component withfive bone cuts and a perpendicular distal bone cut (“Perp 5-Cuts”), anda component with six bone cuts and flexed bone cuts (“Flexed 6-Cuts”);

FIGS. 137A to 137C each illustrate a traditional implant componentoverlaid with each of the three tested implant components;

FIG. 138 illustrate a traditional component overlaid with the 6-Cutsimplant component in an overlaid position that respects the actualimplant placements based on movement of the joint-line;

FIG. 139 illustrate the joint-facing surface of the 6-Cuts implantcomponent positioned on a femur having six corresponding resection cuts;

FIGS. 141A to 141H illustrate various aspects of the FEA testing ofthree femoral implant components;

FIGS. 142A, 142B, and 142C illustrate the FEA-identified high stresslocations for the implant components, which was the same for all threemodels tested;

FIG. 143A illustrates a tibial proximal resection cut that can beselected and/or designed to be a certain distance below a particularlocation on the patient's tibial plateau; FIG. 143B illustrates anatomicsketches (e.g., using a CAD program to manipulate a model of thepatient's biological structure) overlaid with the patient's tibialplateau; FIG. 143C illustrates sketched overlays used to identify thecenters of tubercles and the centers of one or both of the lateral andmedial plateaus;

FIGS. 144A to 144C illustrate one or more axes that can be derived fromanatomic sketches;

FIG. 145A depicts a proximal tibial resection made at 2 mm below thelowest point of the patient's medial tibial plateau with a an A-P slopecut that matched the A-P slope; FIGS. 145B and 145C illustrate animplant selected and/or designed to have 90% coverage of the patient'scut tibial surface;

FIGS. 146A to 156C describe exemplary steps for performing resectioncuts to the tibia using the anatomical references identified above;

FIGS. 157A to 157E illustrate various aspects of an embodiment of atibial implant component, including a view of the tibial tray bottom(FIG. 157A), a view of the tibial tray top (FIG. 157B), a view of thetibial insert bottom (FIG. 157C), a top-front (i.e., proximal-anterior)perspective view of the tibial tray (FIG. 157D), and a bottom front(i.e., distal anterior) perspective view of the tibial insert (FIG.157E);

FIGS. 158A to 158C show aspects of an embodiment of a tibial implantcomponent that includes a tibial tray and a one-piece insert;

FIGS. 159A to 159C show aspects of an embodiment of a tibial implantcomponent that includes a tibial tray and a one-piece insert;

FIGS. 160A to 160C show exemplary steps for altering a blank tibial trayand a blank tibial insert to each include a patient-adapted profile, forexample, to substantially match the profile of the patient's resectedtibial surface;

FIGS. 161A to 161C show exemplary strategies for establishing propertibial rotation for a patient;

FIG. 162 illustrates exemplary stem design options for a tibial tray;

FIGS. 163A and 163B show an approach in certain embodiments foridentifying a tibial implant perimeter profile based on the depth andangle of the proximal tibial resection, which can applied in theselection and/or design of the tibial tray perimeter profile and/or thetibial insert perimeter profile;

FIGS. 164A and 164B show the same approach as described for FIGS. 163Aand 163B, but applied to a different patient having a smaller tibia(e.g., smaller diameter and perimeter length);

FIGS. 165A to 165D show four different exemplary tibial implantprofiles, for example, having different medial and lateral condyleperimeter shapes;

FIGS. 166A and 166B illustrate a first femur jig used to establish pegholes and pin placements for a subsequent jig used for a distal cut;

FIGS. 167A and 167B illustrate a distal femoral resection cut performedwith a second femur jig;

FIG. 168A illustrates an anterior cut, posterior cut, and chamfer cutperformed with a third femur jig; FIG. 168B illustrate an additionalfemoral jig for making additional resection cuts;

FIGS. 169A and 169B illustrate and exemplary tibial jig;

FIG. 170 illustrates and exemplary balancing chip;

FIGS. 171A and 171B illustrate an exemplary balancing chip attached to atibial jig;

FIG. 172 illustrates a first jig used to establish placement andalignment of femoral implant peg holes;

FIG. 173 illustrates a second jig used to establish placement pins forthe distal cut jig;

FIG. 174 illustrates a distal cut jig positioned based on the placementestablished by the previous jig; and

FIG. 175 illustrates remaining resection cuts performed with a chamfercut jig.

Additional figure descriptions are included in the text below. Unlessotherwise denoted in the description for each figure, “M” and “L” incertain figures indicate medial and lateral sides of the view; “A” and“P” in certain figures indicate anterior and posterior sides of theview, and “S” and “I” in certain figures indicate superior and inferiorsides of the view.

DETAILED DESCRIPTION

1. Introduction

When a surgeon uses a traditional off-the-shelf implant to replace apatient's joint, for example, a knee joint, hip joint, or shoulderjoint, certain features of the implant typically do not match theparticular patient's biological features. These mismatches can causevarious complications during and after surgery. For example, surgeonsmay need to extend the surgery time and apply estimates and rules ofthumb during surgery to address the mismatches. For the patient,complications associated with these mismatches can include pain,discomfort, soft tissue impingement, and an unnatural feeling of thejoint during motion, e.g., so-called mid-flexion instability, as well asan altered range of movement and an increased likelihood of implantfailure. In order to fit a traditional implant component to a patient'sarticular bone, surgeons typically remove substantially more of thepatient's bone than is necessary to merely clear diseased bone from thesite. This removal of substantial portions of the patient's bonefrequently diminishes the patient's bone stock to the point that onlyone subsequent revision implant is possible.

Certain embodiments of the implants, guide tools, and related methods ofdesigning (e.g., designing and making), and using the implants and guidetools described herein can be applied to any joint including, withoutlimitation, a spine, spinal articulations, an intervertebral disk, afacet joint, a shoulder, an elbow, a wrist, a hand, a finger, a hip, aknee, an ankle, a foot, or a toe joint. Furthermore, various embodimentsdescribed herein can apply to methods and procedures, and the design ofmethods and procedures, for resectioning the patient's anatomy in orderto implant the implant components described herein and/or to using theguide tools described herein.

1.1 Patient-Adapted Features

Certain embodiments relate to patient-adapted implants, guide tools, andrelated methods. Patient-adapted features of an implant component, guidetool or related implantation method can be achieved by analyzing imagingtest data and selecting and/or designing (e.g., preoperatively selectingfrom a library and/or preoperatively designing) an implant component, aguide tool, and/or a procedure having a feature that is matched and/oroptimized for the particular patient's anatomy and/or biology.Accordingly, the patient-adapted implant components, guide tools, and/ormethods include one or more patient-adapted features. Patient-adaptedfeatures can include patient-specific features and/or patient-engineeredfeatures.

Certain embodiments relate to patient-specific implants, guide tools,and related methods. For example, some embodiments relate to articularimplant components having one or more patient-specific features adaptedto match one or more of the patient's biological features, such as oneor more of biological/anatomical structures, alignments, kinematics,and/or soft tissue impingements. Accordingly, the one or morepatient-specific features of an implant component can include, but arenot limited to, one or more implant component surfaces, such as surfacecontours or angles, and one or more implant component dimensions such asthickness, width, depth, or length. The patient-specific feature(s) ofan implant component can be designed based on patient-specific data tosubstantially match one or more of the patient's biological features(i.e., anatomical and/or biological features). In various embodimentsdescribed herein, the act of designing an implant component can includemanufacturing the implant component having the related design features.For example, designing an implant component can include preoperativelyestablishing a design of one or more features of an implant component,for example, using a CAD computer program on a computer systemspecialized operated for such use and having one or more userinterfaces, and instructing the transfer of that design data, forexample, from a CAD computer program or computer system to a CAM(computer-aided manufacturing) computer program or computer system.Optionally, in certain embodiments, designing the implant can furtherinclude instructing the initiation of manufacturing the physical implantand/or manufacturing the implant.

Alternatively, patient-specific feature(s) of an implant component orguide tool can be achieved by analyzing imaging test data and selecting(e.g., preoperatively selecting from a library of implant components)the implant component that best fits one or more pre-determinedpatient-specific parameters that are derived from the imaging test.

Moreover, an implant component or guide tool can include apatient-specific feature that is both selected and designed. Forexample, an implant component initially can be selected (e.g.,preoperatively selected from a library of implants) to have a featurewith a standard or blank dimension, or with a larger or smallerdimension than the predetermined patient-specific dimension. Then, theimplant component can be machined (if selected from an actual library ofimplant components) or manufactured (if selected from a virtual libraryof implant components) so that the standard dimension or blank dimensionor larger-dimensioned or smaller-dimensioned implant feature is alteredto have the patient-specific dimension.

In addition or alternatively, certain embodiments relate topatient-engineered implants, guide tools, and related methods. Someembodiments relate to articular implant components having one or morepatient-engineered features optimized from patient-specific data to meetone or more parameters to enhance one or more of the patient'sbiological features, such as one or more biological/anatomicalstructures, alignments, kinematics, and/or soft tissue impingements.Accordingly, the one or more patient-engineered features of an implantcomponent can include, but are not limited to, one or more implantcomponent surfaces, such as surface contours, angles or bone cuts, anddimensions such as thickness, width, depth, or length of one or moreaspects of the implant component. The patient-engineered feature(s) ofan implant component can be designed and/or manufactured (e.g.,preoperatively designed and manufactured) based on patient-specific datato substantially enhance or improve one or more of the patient'sanatomical and/or biological features. Methods for preparing certainpatient-engineered features are described, for example, in U.S. Ser. No.12/712,072, entitled “Automated Systems For ManufacturingPatient-Specific Orthopedic Implants And Instrumentation” filed Feb. 24,2010, which is incorporated herein by reference.

As with the patient-specific feature(s) of an implant component or guidetool, the patient-engineered features of an implant component or guidetool can be designed (e.g., preoperatively designed and manufactured) orthey can be selected, for example, by selecting an implant componentthat best meets the one or more predetermined parameters that enhanceone or more features of the patient's biology.

Moreover, an implant component or guide tool can include apatient-engineered feature that is both selected and designed. Forexample, an implant component initially can be selected (e.g.,preoperatively selected from a library of implants) to have a featurewith a larger or smaller dimension than the desired patient-engineereddimension. Then, the implant component can be machined (if selected froman actual library of implant components) or manufactured (if selectedfrom a virtual library of implant components) so that thelarger-dimensioned or smaller-dimensioned implant feature is altered tohave the desired patient-engineered dimension.

1.2 Combinations of Patient-Adapted and Standard Features

A single implant component, guide tool, and/or related method caninclude one or more patient-specific features, one or morepatient-engineered features, and/or one or more standard (e.g.,off-the-shelf features). The standard, off-the-shelf features can beselected to best fit with one or more of the patient-specific and/orpatient-engineered features. For example, in a knee joint, a metalbacked tibial component can include a standard locking mechanism and apatient-adapted (i.e., patient-specific or patient-engineered) perimeterof the tibial component. A patient-specific perimeter of the tibialcomponent can be achieved, for example, by cutting the perimeter of aselected tibial component to match the patient's cortical bone perimeterin one or more dimensions of one more sections. Similarly, apolyethylene insert can be chosen that includes a standard lockingmechanism, while the perimeter is adapted for better support to thepatient's tibial bone perimeter or the perimeter of the metal backing.

In certain aspects, an implant, guide tool, and/or related method caninclude one or more patient-adapted features and one or more standardfeatures. For example, the joint-facing surface of an implant componentcan include a patient-specific feature (e.g., curvature) in the axis oraxes of motion and one or more standard features in other axes. Using acurvature in the direction of motion that is matched to the patient'scurvature (patient-specific) or that is optimized based on the patient'scurvature (patient-engineered) can help to maintain and/or improve thebiomechanical aspects of the patient's joint.

As one illustrative example, in certain embodiments, the joint-facingsurface of a condylar portion of a femoral implant component and/or acorresponding groove in the bearing surface of a tibial implantcomponent can include a patient-specific sagittal curvature (e.g.,having one or more patient-specific radii of curvature) and a standardcoronal curvature or radii of curvature. Coronal radii of curvature alsocan be patient-derived, but an average or an optimum can be derivedacross the articular surface that is constant along the extent of thearticular surface in the coronal plane. The patient-specific sagittalcurvature or radii of curvature can be designed from patient-specificdata to match an existing feature of the patient's biology or it can bepatient-engineered from patient-specific data to improve an existingfeature of the patient's biology.

In certain embodiments, implant components and/or related methodsdescribed herein can include a combination of patient-specific andpatient-engineered features. For example, patient-specific datacollected preoperatively can be used to engineer one or more optimizedsurgical cuts to the patient's bone and to design or select acorresponding implant component having or more bone-facing surfaces orfacets (i.e., “bone cuts”) that specifically match one or more of thepatient's resected bone surfaces. The surgical cuts to the patient'sbone can be optimized (i.e., patient-engineered) to enhance one or moreparameters, such as: (1) deformity correction and limb alignment (2)maximizing preservation of bone, cartilage, or ligaments, (3) maximizingpreservation and/or optimization of other features of the patient'sanatomy, such as trochlea and trochlear shape, (4) restoration and/oroptimization of joint kinematics or biomechanics, (5) restoration oroptimization of joint-line location and/or joint gap width, (6) and/oraddressing one or more other parameters. Based on the optimized surgicalcuts and, optionally, on other desired features of the implantcomponent, the implant component's bone-facing surface can be designedor selected to, at least in part, negatively-match the shape of thepatient's resected bone surface.

Optionally, the implant component can include other patient-adaptedfeatures. For example; the joint-facing surface can be designed to, atleast in part, substantially negatively-match an opposing surface at thejoint cavity (e.g., the surface of the patient's biological structure,native or resected, or the surface of an opposing implant component. Incertain embodiments, the joint-facing surface of the implant componentcan include patient-adapted features such as a patient-specific sagittalcurvature and a patient-engineered coronal curvature, or apatient-specific sagittal curvature and a patient-specific coronalcurvature. These curvatures can be patient-specific in at least aportion or the entire joint-facing surface of the implant. Alternativelyor in addition, one or more of these curvatures can be patient-adaptedin one condyle, but not patient-adapted in the other condyle. Moreover,the shape (e.g., curvature) of a first condyle can be used, for example,to generate a shape (e.g., curvature) for the second condyle.

1.3 Implant Systems

An implant (i.e., an implant system) can include one or more implantcomponents, which, as described above, can each include one or morepatient-specific features, one or more patient-engineered features, andone or more standard (e.g., off-the-shelf) features. Moreover, animplant system can include one or more patient-adapted (e.g.,patient-specific and/or patient-engineered) implant components and oneor more standard implant components.

For example, a knee implant can include a femoral implant componenthaving one or more patient-adapted and standard features, and anoff-the-shelf tibial implant component having only standard features. Inthis example, the entire tibial implant component can be off-the-shelf.Alternatively, a metal-backed implant component (or portion of animplant component) can be patient-specific, e.g., matched in the A-Pdimension or the M-L dimension to the patient's tibial cortical bone,while the corresponding plastic insert implant component (orcorresponding portion of the implant component) can include a standardoff-the-shelf configuration.

Off-the-shelf configuration can mean that the tibial insert has fixed,standard dimensions to fit, for example, into a standard tibial tray.Off-the-shelf configuration also can mean that the tibial insert has afixed, standard dimension or distance between two tibial dishes orcurvatures to accommodate the femoral bearing surface. The latterconfiguration is particularly applicable in an implant system that usesa femoral implant component that is patient-specifically matched in theM-L dimension to the distal femur of the patient's bone, but uses astandardized intercondylar notch width on the femoral component toachieve optimal mating with a corresponding tibial insert. For example,FIGS. 1A and 1B show schematic representations in a coronal plane of apatient's distal femur (FIG. 1A) and a femoral implant component (FIG.1B). As shown in the figures, the implant component M-L dimension 100(e.g. epicondylar M-L dimension) patient-specifically matches thecorresponding M-L dimension of the patient's femur 102. However, theintercondylar M-L dimension (i.e., notch width) of the implantcomponent, 104, can be standard, which in this figure is shorter thanthe patient's intercondylar M-L dimension 106. In this way, theepicondylar M-L dimension of the implant component is patient-specific,while the intercondylar M-L dimension (i.e., notch width) is designed tobe a standard length, for example, so that is can properly engage duringjoint motion a tibial insert having a standard distance between itsdishes or curvatures that engage the condyles of the femoral implantcomponent.

1.4 Improved Implants, Guide Tools and Related Methods

Certain embodiments are directed to implants, guide tools, and/orrelated methods that can be used to provide to a patient a pre-primaryprocedure and/or a pre-primary implant such that a subsequent,replacement implant can be performed with a second (and, optionally, athird, and optionally, a fourth) patient-adapted pre-primary implant orwith a traditional primary implant. In certain embodiments, thepre-primary implant procedure can include 3, 4, 5, 6, 7, or moreresection or surgical cuts to the patient's bone and the pre-primaryimplant can include on its corresponding bone-facing surface a matchingnumber and orientation of bone-cut facets or surfaces.

In one illustrative embodiment, a first pre-primary joint-replacementprocedure includes a patient-adapted implant component, guide tool,and/or related method. The patient-adapted implant component, guidetool, and/or related method can be preoperatively selected and/ordesigned from patient-specific data, such as one or more images of thepatient's joint, to include one or more features that arepatient-specific or patient-engineered. The features (e.g., dimensions,shape, surface contours) of the first pre-primary implant and,optionally, patient-specific data (e.g., features of the patient'sresected bone surfaces and features of the patient's contralateraljoint) can be stored in a database. When the first pre-primary implantfails, for example, due to bone loss or osteolysis or aseptic looseningat a later point in time (e.g., 15 years after the originalimplantation) a second implant can be implanted. For the second implantprocedure, the amount of diseased bone can be assessed. If the amount ofdiseased bone to be resected is minimal, the patient-specific data canbe used to select and/or design a second pre-primary procedure and/or apre-primary implant. If the amount of diseased bone to be resected issubstantial, a traditional primary procedure and a traditional implantcan be employed.

Alternatively, certain embodiments are directed to implants, guidetools, and/or related methods that can be used to provide to a patient aprimary procedure and/or a primary implant such that a subsequentreplacement implant can be used as part of a traditional revisionprocedure. Certain embodiments are directed to implants, guide tools,and/or related methods that can be used to provide a patient-adaptedrevision implant. For example, following a traditional implant, asubsequent revision can include a patient-adapted procedure and/or apatient-adapted implant component as described herein.

FIG. 2 is a flow chart illustrating a process that includes selectingand/or designing a first patient-adapted implant, for example, apre-primary implant. First, using the techniques described herein orthose suitable and known in the art, measurements of the target jointare obtained 210. This step can be repeated multiple times, as desired.Optionally, a virtual model of the joint can be generated, for example,to determine proper joint alignment and the corresponding resection cutsand implant component features based on the determined proper alignment.This information can be collected and stored 212 in a database 213. Oncemeasurements of the target joint are obtained and analyzed to determineresection cuts and patient-adapted implant features, the patient-adaptedimplant components can be selected 214 (e.g., selected from a virtuallibrary and optionally manufactured without further design alteration215, or selected from a physical library of implant components).Alternatively, or in addition, one or more implant components withbest-fitting and/or optimized features can be selected 214 (e.g., from alibrary) and then further designed (e.g., designed and manufactured)216. Alternatively or in addition, one or more implant components withbest-fitting and/or optimized features can be designed (e.g., designedand manufactured) 218, 216 without an initial selection from a library.Using a virtual model to assess the selected or designed implantcomponent(s), this process also can be repeated as desired (e.g., beforeone or more physical components are selected and/or generated). Theinformation regarding the selected and/or designed implant component(s)can be collected and stored 220, 222 in a database 213. Once a desiredfirst patient-adapted implant component or set of implant components isobtained, a surgeon can prepare the implantation site and install thefirst implant 224. The information regarding preparation of theimplantation site and implant installation can be collected and stored226 in a database 213. In this way, the information associated with thefirst pre-primary implant component is available for use by a surgeonfor subsequent implantation of a second pre-primary or a primaryimplant.

FIG. 3 is a flow chart illustrating a process that includes selectingand/or designing a second implant. In certain embodiments, the secondimplant can be a traditional primary implant. Alternatively, the secondimplant can be a patient-adapted implant, which optionally can be usedas second pre-primary implant that allows for a subsequent (i.e., third)primary implant using a traditional implant.

The steps described in FIG. 3 are similar to those described above for afirst pre-primary implant (see FIG. 2); however, in the second implantprocess, the database information 213 collected and stored in the firstimplant process can be used as part of the process for the secondimplant. In addition to the database information from the first implantprocess 213, additional measurements of the target joint optionally canbe obtained 310 and used together with the database information 213 fromthe first implant process as a basis for selecting and/or designing asecond implant. This step can be repeated multiple times, as desired.Optionally, a virtual model of the joint can be generated (with ourwithout a model of the first implant), for example, to determine properjoint alignment, corresponding resection cuts and, optionally,patient-adapted implant component features based on the determinedproper alignment. This information can be collected and stored 312 asnew or additional database information 313. Once the databaseinformation from the first implant process and optionally newmeasurements of the target joint and first implant are obtained andanalyzed, the implant component(s) for the second implant can beselected 314 (e.g., selected from a virtual library and optionallymanufactured without further design alteration 315, or selected from aphysical library of implant components, or selected from amongtraditional implant components). Alternatively or in addition, one ormore implant components with best-fitting and/or optimized features canbe selected 314 (e.g., from a library) and then further designed (e.g.,designed and manufactured) 316. Alternatively or in addition, one ormore implant components with best-fitting and/or optimized features canbe designed (e.g., designed and manufactured) 038 without an initialselection from a library. Using a virtual model to assess the selectedor designed implant component, this process also can be repeated asdesired (e.g., before one or more physical components are selectedand/or generated). The information regarding the selected and/ordesigned implant components for the second implant can be collected andstored 320, 322 in a database 313. Once a desired implant component orset of implant components is obtained for the second implant, a surgeoncan prepare the implantation site, including removing the first implant,and install the second implant 324. The information regardingpreparation of the implantation site and second implant installation canbe collected and stored 326 in a database 313.

The second implant can have standard attachment mechanisms, e.g., a stemand or pegs or other attachment means known in the art. Alternatively,the attachment mechanisms can be patient-specific by deriving shapeinformation on the residual bone, e.g., of a femur and acetabulum or ofa femur and a tibia or of a humerus and a glenoid, using image data,e.g., CT or MRI data. One or more dimensions or shapes or joint-facingsurfaces of the second implant can be adapted to include, at least inpart, information reflective of the corresponding dimension(s) orshape(s) or joint-facing surface(s) of the first implant. In thismanner, a better functional result can be achieved with the revisionimplant by maintaining patient-specific shapes and/or geometry in therevision implant by accessing data in the patient database.

Accordingly, certain embodiments described herein are directed toimplants, implant components, guide tools, and related methods thataddress many of the problems associated with traditional implants, suchas mismatches between an implant component and a patient's biologicalfeatures (e.g., a feature of a biological structure, a distance or spacebetween two biological structures, and/or a feature associated withanatomical function) and substantial bone removal that limits subsequentrevisions following a traditional primary implant.

2. Exemplary Implant Systems and Patient-Adapted Features

The concepts described herein can be embodied in various types ofarticular implants including, but not limited to, knee-joint implants,hip-joint implants, shoulder-joint implants, and spinal implants (e.g.,intervertebral implants and facet joint implants), as well as relatedsurgical tools (e.g., guide tools) and methods. Exemplary traditionalimplants are illustrated in FIGS. 4A-4M. In particular, FIGS. 4A and 4Billustrate exemplary traditional knee-joint implants as described, forexample, in U.S. Pat. Nos. 5,824,105 and 5,133,758, respectively; FIGS.4C-4G illustrate traditional hip-joint implants, including AustinMoore-type, Thompson-type, and Bipolar hip-type prostheses; FIGS. 4H-4Jillustrate traditional shoulder-joint implants as described, forexample, in U.S. Pat. No. 7,175,663; and FIGS. 4K-4M illustratetraditional spinal implants, as described, for example, in U.S. Pat. No.7,166,129 and at the web site, www.facetsolutions.com/AFRSproduct.html.

In certain embodiments described herein, an implant or implant systemcan include one, two, three, four or more components having one or morepatient-specific features that substantially match one or more of thepatient's biological features, for example, one or more dimensionsand/or measurements of an anatomical/biological structure, such as bone,cartilage, tendon, or muscle; a distance or space between two or moreaspects of a biological structure and/or between two or more differentbiological structures; and a biomechanical or kinematic quality ormeasurement of the patient's biology. In addition or alternatively, animplant component can include one or more features that are engineeredto optimize or enhance one or more of the patient's biological features,for example, (1) deformity correction and limb alignment (2) preservingbone, cartilage, and/or ligaments, (3) preserving and/or optimizingother features of the patient's anatomy, such as trochlea and trochlearshape, (4) restoring and/or optimizing joint kinematics or biomechanics,and/or (5) restoring and/or optimizing joint-line location and/or jointgap width. In addition, an implant component can be designed and/ormanufactured to include one or more standard (i.e., non-patient-adapted)features.

Exemplary patient-adapted (i.e., patient-specific and/orpatient-engineered) features of the implant components described hereinare identified in Table 1. One or more of these implant componentfeatures can be selected and/or designed based on patient-specific data,such as image data.

TABLE 1 Exemplary implant features that can be patient- adapted based onpatient-specific measurements Category Exemplary feature Implant orimplant One or more portions of, or all of, an external or componentimplant component curvature (applies knee, One or more portions of, orall of, an internal shoulder, hip, implant dimension ankle, or other Oneor more portions of, or all of, an internal or implant or implantexternal implant angle component) Portions or all of one or more of theML, AP, SI dimension of the internal and external component andcomponent features An outer locking mechanism dimension between aplastic or non-metallic insert and a metal backing component in one ormore dimensions Component height Component profile Component 2D or 3Dshape Component volume Composite implant height Insert width Insertshape Insert length Insert height Insert profile Insert curvature Insertangle Distance between two curvatures or concavities Polyethylene orplastic width Polyethylene or plastic shape Polyethylene or plasticlength Polyethylene or plastic height Polyethylene or plastic profilePolyethylene or plastic curvature Polyethylene or plastic angleComponent stem width Component stem shape Component stem lengthComponent stem height Component stem profile Component stem curvatureComponent stem position Component stem thickness Component stem angleComponent peg width Component peg shape Component peg length Componentpeg height Component peg profile Component peg curvature Component pegposition Component peg thickness Component peg angle Slope of an implantsurface Number of sections, facets, or cuts on an implant surfaceFemoral implant or Condylar distance of a femoral component, e.g.,implant component between femoral condyles A condylar coronal radius ofa femoral component A condylar sagittal radius of a femoral componentTibial implant or Slope of an implant surface implant component Condylardistance, e.g., between tibial joint-facing surface concavities thatengage femoral condyles Coronal curvature (e.g., one or more radii ofcurvature in the coronal plane) of one or both joint-facing surfaceconcavities that engage each femoral condyle Sagittal curvature (e.g.,one or more radii of curvature in the sagittal plane) of one or bothjoint-facing surface concavities that engage each femoral condyle

The patient-adapted features described in Table 1 also can be applied topatient-adapted guide tools described herein.

The patient-adapted implant components and guide tools described hereincan include any number of patient-specific features, patient-engineeredfeatures, and/or standard features. Illustrative combinations ofpatient-specific, patient-engineered, and standard features of animplant component are provided in Table 2. Specifically, the tableillustrates an implant or implant component having at least thirteendifferent features. Each feature can be patient-specific (P),patient-engineered (PE), or standard (St). As shown, there are 105unique combinations in which each of thirteen is eitherpatient-specific, patient-engineered, or standard features.

TABLE 2 Exemplary combinations of patient-specific (P),patient-engineered (PE), and standard (St) features¹ in an implantImplant system Implant feature number² number 1 2 3 4 5 6 7 8 9 10 11 1213 1 P P P P P P P P P P P P P 2 PE PE PE PE PE PE PE PE PE PE PE PE PE3 St St St St St St St St St St St St St 4 P St St St St St St St St StSt St St 5 P P St St St St St St St St St St St 6 P P P St St St St StSt St St St St 7 P P P P St St St St St St St St St 8 P P P P P St St StSt St St St St 9 P P P P P P St St St St St St St 10 P P P P P P P St StSt St St St 11 P P P P P P P P St St St St St 12 P P P P P P P P P St StSt St 13 P P P P P P P P P P St St St 14 P P P P P P P P P P P St St 15P P P P P P P P P P P P St 16 P PE PE PE PE PE PE PE PE PE PE PE PE 17 PP PE PE PE PE PE PE PE PE PE PE PE 18 P P P PE PE PE PE PE PE PE PE PEPE 19 P P P P PE PE PE PE PE PE PE PE PE 20 P P P P P PE PE PE PE PE PEPE PE 21 P P P P P P PE PE PE PE PE PE PE 22 P P P P P P P PE PE PE PEPE PE 23 P P P P P P P P PE PE PE PE PE 24 P P P P P P P P P PE PE PE PE25 P P P P P P P P P P PE PE PE 26 P P P P P P P P P P P PE PE 27 P P PP P P P P P P P P PE 28 PE St St St St St St St St St St St St 29 PE PESt St St St St St St St St St St 30 PE PE PE St St St St St St St St StSt 31 PE PE PE PE St St St St St St St St St 32 PE PE PE PE PE St St StSt St St St St 33 PE PE PE PE PE PE St St St St St St St 34 PE PE PE PEPE PE PE St St St St St St 35 PE PE PE PE PE PE PE PE St St St St St 36PE PE PE PE PE PE PE PE PE St St St St 37 PE PE PE PE PE PE PE PE PE PESt St St 38 PE PE PE PE PE PE PE PE PE PE PE St St 39 PE PE PE PE PE PEPE PE PE PE PE PE St 40 P PE St St St St St St St St St St St 41 P PE PESt St St St St St St St St St 42 P PE PE PE St St St St St St St St St43 P PE PE PE PE St St St St St St St St 44 P PE PE PE PE PE St St St StSt St St 45 P PE PE PE PE PE PE St St St St St St 46 P PE PE PE PE PE PEPE St St St St St 47 P PE PE PE PE PE PE PE PE St St St St 48 P PE PE PEPE PE PE PE PE PE St St St 49 P PE PE PE PE PE PE PE PE PE PE St St 50 PPE PE PE PE PE PE PE PE PE PE PE St 51 P P PE St St St St St St St St StSt 52 P P PE PE St St St St St St St St St 53 P P PE PE PE St St St StSt St St St 54 P P PE PE PE PE St St St St St St St 55 P P PE PE PE PEPE St St St St St St 56 P P PE PE PE PE PE PE St St St St St 57 P P PEPE PE PE PE PE PE St St St St 58 P P PE PE PE PE PE PE PE PE St St St 59P P PE PE PE PE PE PE PE PE PE St St 60 P P PE PE PE PE PE PE PE PE PEPE St 61 P P P PE St St St St St St St St St 62 P P P PE PE St St St StSt St St St 63 P P P PE PE PE St St St St St St St 64 P P P PE PE PE PESt St St St St St 65 P P P PE PE PE PE PE St St St St St 66 P P P PE PEPE PE PE PE St St St St 67 P P P PE PE PE PE PE PE PE St St St 68 P P PPE PE PE PE PE PE PE PE St St 69 P P P PE PE PE PE PE PE PE PE PE St 70P P P P PE St St St St St St St St 71 P P P P PE PE St St St St St St St72 P P P P PE PE PE St St St St St St 73 P P P P PE PE PE PE St St St StSt 74 P P P P PE PE PE PE PE St St St St 75 P P P P PE PE PE PE PE PE StSt St 76 P P P P PE PE PE PE PE PE PE St St 77 P P P P PE PE PE PE PE PEPE PE St 78 P P P P P PE St St St St St St St 79 P P P P P PE PE St StSt St St St 80 P P P P P PE PE PE St St St St St 81 P P P P P PE PE PEPE St St St St 82 P P P P P PE PE PE PE PE St St St 83 P P P P P PE PEPE PE PE PE St St 84 P P P P P PE PE PE PE PE PE PE St 85 P P P P P P PESt St St St St St 86 P P P P P P PE PE St St St St St 87 P P P P P P PEPE PE St St St St 88 P P P P P P PE PE PE PE St St St 89 P P P P P P PEPE PE PE PE St St 90 P P P P P P PE PE PE PE PE PE St 91 P P P P P P PPE St St St St St 92 P P P P P P P PE PE St St St St 93 P P P P P P P PEPE PE St St St 94 P P P P P P P PE PE PE PE St St 95 P P P P P P P PE PEPE PE PE St 96 P P P P P P P P PE St St St St 97 P P P P P P P P PE PESt St St 98 P P P P P P P P PE PE PE St St 99 P P P P P P P P PE PE PEPE St 100 P P P P P P P P P PE St St St 101 P P P P P P P P P PE PE StSt 102 P P P P P P P P P PE PE PE St 103 P P P P P P P P P P PE St St104 P P P P P P P P P P PE PE St 105 P P P P P P P P P P P PE St ¹S =standard, off-the-shelf, P = patient-specific, PE = patient-engineered(e.g., constant coronal curvature, derived from the patient's coronalcurvatures along articular surface) ²Each of the thirteen numberedimplant features represents a different exemplary implant feature, forexample, for a knee implant the thirteen features can include: (1)femoral implant component M-L dimension, (2) femoral implant componentA-P dimension, (3) femoral implant component bone cut, (4) femoralimplant component sagittal curvature, (5) femoral implant componentcoronal curvature, (6) femoral implant component inter-condylardistance, (7) femoral implant component notch location/geometry, (8)tibial implant component M-L dimension, (9) tibial implant component A-Pdimension, (10) tibial implant component insert inter-condylar distance,(11) tibial implant component insert lock, (12) tibial implant componentmetal backing lock, and (13) tibial implant component metal backingperimeter.

The term “implant component” as used herein can include: (i) one of twoor more devices that work together in an implant or implant system, or(ii) a complete implant or implant system, for example, in embodimentsin which an implant is a single, unitary device. The term “match” asused herein is envisioned to include one or both of a negative-match, asa convex surface fits a concave surface, and a positive-match, as onesurface is identical to another surface.

Three illustrative embodiments of implants and/or implant components areschematically represented in FIGS. 5A-5C. In FIG. 5A, the illustrativeimplant component 500 includes an inner, bone-facing surface 502 and anouter, joint-facing surface 504. The inner bone-facing surface 502engages a first articular surface 510 of a first biological structure512, such as bone or cartilage, at a first interface 514. The articularsurface 510 can be a native surface, a resected surface, or acombination of the two. The outer, joint-facing surface 504 opposes asecond articular surface 520 of a second biological structure 522 at ajoint interface 524. The dashed line across each figure illustrates apatient's joint-line. In certain embodiments, one or more features ofthe implant component, for example, an M-L, A-P, or S-I dimension, afeature of the inner, bone-facing surface 502, and/or a feature of theouter, joint-facing surface 504, are patient-adapted (i.e., include oneor more patient-specific and/or patient-engineered features).

The illustrative embodiment shown in FIG. 5B includes two implantcomponents 500, 500′. Each implant component 500, 500′ includes aninner, bone-facing surface 502, 502′ and an outer, joint-facing surface504, 504′. The first inner, bone-facing surface 502 engages a firstarticular surface 510 of a first biological structure 512 (e.g., bone orcartilage) at a first interface 514. The first articular surface 510 canbe a native surface, a cut surface, or a combination of the two. Thesecond bone-facing surface 502′ engages a second articular surface 520of a second biological structure 522 at a second interface 514′. Thesecond articular surface 520 can be a native surface, a resectedsurface, or a combination of the two. In addition, an outer,joint-facing surface 504 on the first component 500 opposes a second,outer joint-facing surface 504′ on the second component 500′ at thejoint interface 524. In certain embodiments, one or more features of theimplant component, for example, one or both of the inner, bone-facingsurfaces 502, 502′ and/or one or both of the outer, joint-facingsurfaces 504, 504′, are patient-adapted (i.e., include one or morepatient-specific and/or patient-engineered features).

The illustrative embodiment represented in FIG. 5C includes the twoimplant components 500, 500′, the two biological structures 512, 522,the two interfaces 514, 514′, and the joint interface 524, as well asthe corresponding surfaces, as described for the embodiment illustratedin FIG. 5B. However, FIG. 5C also includes structure 550, which can bean implant component in certain embodiments or a biological structure incertain embodiments. Accordingly, the presence of a third structural 550surface in the joint creates a second joint interface 524′, and possiblya third 524″, in addition to joint interface 524. Alternatively or inaddition to the patient-adapted features described above for components500 and 500′, the components 500, 500′ can include one or more features,such as surface features at the additional joint interface(s) 524, 524″,as well as other dimensions (e.g., height, width, depth, contours, andother dimensions) that are patient-adapted, in whole or in part.Moreover, structure 550, when it is an implant component, also can haveone or more patient-adapted features, such as one or morepatient-adapted surfaces and dimensions.

Traditional implants and implant components can have surfaces anddimensions that are a poor match to a particular patient's biologicalfeature(s). The patient-adapted implants, guide tools, and relatedmethods described herein improve upon these deficiencies. The followingtwo subsections describe two particular improvements, with respect tothe bone-facing surface and the joint-facing surface of an implantcomponent; however, the principles described herein are applicable toany aspect of an implant component.

2.1 Bone-Facing Surface of an Implant Component

In certain embodiments, the bone-facing surface of an implant can bedesigned to substantially negatively-match one more bone surfaces. Forexample, in certain embodiments at least a portion of the bone-facingsurface of a patient-adapted implant component can be designed tosubstantially negatively-match the shape of subchondral bone, corticalbone, endosteal bone, and/or bone marrow. A portion of the implant alsocan be designed for resurfacing, for example, by negatively-matchingportions of a bone-facing surface of the implant component to thesubchondral bone or cartilage. Accordingly, in certain embodiments, thebone-facing surface of an implant component can include one or moreportions designed to engage resurfaced bone, for example, by having asurface that negatively-matches uncut subchondral bone or cartilage, andone or more portions designed to engage cut bone, for example, by havinga surface that negatively-matches a cut subchondral bone.

In certain embodiments, the bone-facing surface of an implant componentincludes multiple surfaces, also referred to herein as bone cuts. One ormore of the bone cuts on the bone-facing surface of the implantcomponent can be selected and/or designed to substantiallynegatively-match one or more surfaces of the patient's bone. Thesurface(s) of the patient's bone can include bone, cartilage, or otherbiological surfaces. For example, in certain embodiments, one or more ofthe bone cuts on the bone-facing surface of the implant component can bedesigned to substantially negatively-match (e.g., the number, depth,and/or angles of cut) one or more resected surfaces of the patient'sbone. The bone-facing surface of the implant component can include anynumber of bone cuts, for example, two, three, four, less than five,five, more than five, six, seven, eight, nine or more bone cuts. Incertain embodiments, the bone cuts of the implant component and/or theresection cuts to the patient's bone can include one or more facets oncorresponding portions of an implant component. For example, the facetscan be separated by a space or by a step cut connecting twocorresponding facets that reside on parallel or non-parallel planes.These bone-facing surface features can be applied to various jointimplants, including knee, hip, spine, and shoulder joint implants.

FIG. 6A illustrates an exemplary femoral implant component 600 havingsix bone cuts. FIG. 6B illustrates a femoral implant component 600having seven bone cuts. In FIG. 6A and FIG. 6B, the six or sevenrespective bone cuts are identified by arrows on the inner, bone-facingsurface 602 of the implant component 600. The bone cuts can include, forexample, an anterior bone cut A, a distal bone cut D, and a posteriorbone cut P, as well as one or more anterior chamfer bone cuts betweenthe anterior bone cut A and distal bone cut D, and/or one or moreposterior chamfer bone cuts between the distal posterior bone cut P andthe distal bone cut D. The implant component depicted in FIG. 6Aincludes one anterior chamfer bone cut and two posterior chamfer bonecuts, in addition to anterior, posterior and distal bone cuts. Theimplant component depicted in FIG. 6B includes two anterior chamfer bonecuts and two posterior chamfer bone cuts, in addition to anterior,posterior and distal bone cuts.

Any one or more bone cuts can include one or more facets. For example,the implant components exemplified in FIG. 6A and FIG. 6B depictcorresponding condylar facets for each of the distal bone cut, posteriorbone cut, first posterior chamfer bone cut and second posterior chamferbone cut. In FIG. 6A, distal bone cut facets on lateral and medialcondyles are identified by 604 and 606, respectively. Facets of a bonecut can be separated by a space between corresponding regions of animplant component, as exemplified by the condylar facets separated bythe intercondylar space 608 in FIG. 6A and FIG. 6B. Alternatively or inaddition, facets of a bone cut can be separated by a step cut, forexample, a vertical or angled cut connecting two non-coplanar or nonfacets of a bone cut. As shown by the implant components exemplified ineach of FIG. 6A and FIG. 6B, each bone cut and/or bone cut facet can besubstantially planar. Two substantially planar facets of the same bonecut can be non-coplanar (i.e., not lying in the same cut plane) and/ornon-parallel (i.e., not lying in the same cut plane and not lying in asubstantially parallel cut plane).

In certain embodiments, one or more bone cut facets, bone cuts, and/orthe entire bone-facing surface of an implant can be non-planar, forexample, substantially curvilinear. FIG. 6C illustrates a femoralimplant component 610 having two planar bone cuts 612 and onecurvilinear bone cut 614. In the figure, the femoral implant component610 is shown attached to resected surfaces 616 of a femur 618.

In certain embodiments, corresponding sections of an implant componentcan include different thicknesses (i.e., distance between thecomponent's bone-facing surface and joint-facing surface), surfacefeatures, bone cut features, section volumes, and/or other features. Forexample, as shown in FIG. 6A, the corresponding distal lateral andmedial sections of the implant, identified by 604 and 606 on theirrespective bone cut facets, include different thicknesses, sectionvolumes, bone cut angles, and bone cut surface areas. As this exampleillustrates, one or more of the thicknesses, section volumes, bone cutangles, bone cut surface areas, bone cut curvatures, numbers of bonecuts, peg placements, peg angles, and other features may vary betweentwo or more sections (e.g., corresponding sections on lateral and medialcondyles) of an implant component. Alternatively or in addition, one,more, or all of these features can be the same in corresponding sectionsof an implant component. An implant design that allows for independentfeatures on different sections of an implant allows various options forachieving one or more goals, including, for example, (1) deformitycorrection and limb alignment (2) preserving bone, cartilage, and/orligaments, (3) preserving and/or optimizing other features of thepatient's anatomy, such as trochlea and trochlear shape, (4) restoringand/or optimizing joint kinematics or biomechanics, and/or (5) restoringand/or optimizing joint-line location and/or joint gap width.

In certain embodiments, it can be advantageous to maintain certainfeatures across different portions of an implant component, whilevarying certain other features. For example, two or more correspondingsections of an implant component can include the same implantthickness(es). As a specific example, with a femoral implant component,corresponding medial and lateral sections of the implant's condyles(e.g., distal medial and lateral condyle and/or posterior medial andlateral condyles) can be designed to include the same thickness or atleast a threshold thickness, particularly the bone cut intersections.Alternatively or in addition, every section on the medial and lateralcondyles can be designed to include the same thickness or at least athreshold thickness. This approach is particularly useful when thecorresponding implant sections are exposed to similar stress forces andtherefore require similar minimum thicknesses in response to thosestresses. Alternatively or in addition, an implant design can include arule, such that a quantifiable feature of one section is always greaterthan, greater than or equal to, less than, or less than or equal to thesame feature of another section of the implant component. For example,in certain embodiments, an implant design can include a lateral distaland/or posterior condylar portion that is thicker than or equal inthickness to the corresponding medial distal and/or posterior condylarportion. Similarly, in certain embodiments, an implant design caninclude a lateral distal posterior condyle height that is higher than orequal to the corresponding medial posterior condylar height.

In certain embodiments, one or more of an implant component's bone cutor bone cut facet features (e.g., thickness, section volume, cut angle,surface area, and/or other features) can be patient-adapted. Forexample, as described more fully below, patient-specific data, such asimaging data of a patient's joint, can be used to select and/or designan implant component (and, optionally, a corresponding surgicalprocedure and/or surgical tool) that matches a patient's anatomy and/oroptimizes a parameter of that patient's anatomy. Alternatively or inaddition, one or more aspects of an implant component, for example, oneor more bone cuts, can be selected and/or designed to matchpredetermined resection cuts. Predetermined as used herein includes, forexample, preoperatively determined (e.g., preoperatively selected and/ordesigned). For example, predetermined resection cuts can includeresection cuts determined preoperatively, optionally as part of theselection and/or design of one or more implant components and/or one ormore guide tools. Similarly, a surgical guide tool can be selectedand/or designed to guide the predetermined resection cuts. For example,the resection cuts and matching component bone cuts (and, optionally, aguide tool) can be selected and/or designed, for example, to removediseased or malformed tissue and/or to optimize a desired anatomicaland/or kinematic parameter, such as maximizing bone preservation,correcting a joint and/or alignment deformity, enhancing jointkinematics, enhancing or preserving joint-line location, and/or otherparameter(s) described herein.

2.2 Joint-Facing Surface of an Implant Component

In various embodiments described herein, the outer, joint-facing surfaceof an implant component includes one or more patient-adapted (e.g.,patient-specific and/or patient-engineered features). For example, incertain embodiments, the joint-facing surface of an implant componentcan be designed to match the shape of the patient's biologicalstructure.

The joint-facing surface can include, for example, the bearing surfaceportion of the implant component that engages an opposing biologicalstructure or implant component in the joint to facilitate typicalmovement of the joint. The patient's biological structure can include,for example, cartilage, bone, and/or one or more other biologicalstructures.

For example, in certain embodiments, the joint-facing surface of animplant component is designed to match the shape of the patient'sarticular cartilage. For example, the joint-facing surface cansubstantially positively-match one or more features of the patient'sexisting cartilage surface and/or healthy cartilage surface and/or acalculated cartilage surface, on the articular surface that thecomponent replaces. Alternatively, it can substantially negatively-matchone or more features of the patient's existing cartilage surface and/orhealthy cartilage surface and/or a calculated cartilage surface, on theopposing articular surface in the joint. As described below, correctionscan be performed to the shape of diseased cartilage by designingsurgical steps (and, optionally, patient-adapted surgical tools) tore-establish a normal or near normal cartilage shape that can then beincorporated into the shape of the joint-facing surface of thecomponent. These corrections can be implemented and, optionally, testedin virtual two-dimensional and three-dimensional models. The correctionsand testing can include kinematic analysis and/or surgical steps.

In certain embodiments, the joint-facing surface of an implant componentcan be designed to positively-match the shape of subchondral bone. Forexample, the joint-facing surface of an implant component cansubstantially positively-match one or more features of the patient'sexisting subchondral bone surface and/or healthy subchondral bonesurface and/or a calculated subchondral bone surface, on the articularsurface that the component attaches to on its bone-facing surface.Alternatively, it can substantially negatively-match one or morefeatures of the patient's existing subchondral bone surface and/orhealthy subchondral bone surface and/or a calculated subchondral bonesurface, on the opposing articular surface in the joint. Corrections canbe performed to the shape of subchondral bone to re-establish a normalor near normal articular shape that can be incorporated into the shapeof the component's joint-facing surface. A standard thickness can beadded to the joint-facing surface, for example, to reflect an averagecartilage thickness. Alternatively, a variable thickness can be appliedto the component. The variable thickness can be selected to reflect apatient's actual or healthy cartilage thickness, for example, asmeasured in the individual patient or selected from a standard referencedatabase.

In certain embodiments, the joint-facing surface of an implant componentcan include one or more standard features. The standard shape of thejoint-facing surface of the component can reflect, at least in part, theshape of typical healthy subchondral bone or cartilage. For example, thejoint-facing surface of an implant component can include a curvaturehaving standard radii or curvature of in one or more directions.Alternatively or in addition, an implant component can have a standardthickness or a standard minimum thickness in select areas. Standardthickness(es) can be added to one or more sections of the joint-facingsurface of the component or, alternatively, a variable thickness can beapplied to the implant component.

Certain embodiments, such as those illustrated by FIGS. 5B and 5C,include, in addition to a first implant component, a second implantcomponent having an opposing joint-facing surface. The second implantcomponent's bone-facing surface and/or joint-facing surface can bedesigned as described above. Moreover, in certain embodiments, thejoint-facing surface of the second component can be designed, at leastin part, to match (e.g., substantially negatively-match) thejoint-facing surface of the first component. Designing the joint-facingsurface of the second component to complement the joint-facing surfaceof the first component can help reduce implant wear and optimizekinematics. Thus, in certain embodiments, the joint-facing surfaces ofthe first and second implant components can include features that do notmatch the patient's existing anatomy, but instead negatively-match ornearly negatively-match the joint-facing surface of the opposing implantcomponent.

However, when a first implant component's joint-facing surface includesa feature adapted to a patient's biological feature, a second implantcomponent having a feature designed to match that feature of the firstimplant component also is adapted to the patient's same biologicalfeature. By way of illustration, when a joint-facing surface of a firstcomponent is adapted to a portion of the patient's cartilage shape, theopposing joint-facing surface of the second component designed to matchthat feature of the first implant component also is adapted to thepatient's cartilage shape. When the joint-facing surface of the firstcomponent is adapted to a portion of a patient's subchondral bone shape,the opposing joint-facing surface of the second component designed tomatch that feature of the first implant component also is adapted to thepatient's subchondral bone shape. When the joint-facing surface of thefirst component is adapted to a portion of a patient's cortical bone,the joint-facing surface of the second component designed to match thatfeature of the first implant component also is adapted to the patient'scortical bone shape. When the joint-facing surface of the firstcomponent is adapted to a portion of a patient's endosteal bone shape,the opposing joint-facing surface of the second component designed tomatch that feature of the first implant component also is adapted to thepatient's endosteal bone shape. When the joint-facing surface of thefirst component is adapted to a portion of a patient's bone marrowshape, the opposing joint-facing surface of the second componentdesigned to match that feature of the first implant component also isadapted to the patient's bone marrow shape.

The opposing joint-facing surface of a second component cansubstantially negatively-match the joint-facing surface of the firstcomponent in one plane or dimension, in two planes or dimensions, inthree planes or dimensions, or in several planes or dimensions. Forexample, the opposing joint-facing surface of the second component cansubstantially negatively-match the joint-facing surface of the firstcomponent in the coronal plane only, in the sagittal plane only, or inboth the coronal and sagittal planes.

In creating a substantially negatively-matching contour on an opposingjoint-facing surface of a second component, geometric considerations canimprove wear between the first and second components. For example, theradii of a concave curvature on the opposing joint-facing surface of thesecond component can be selected to match or to be slightly larger inone or more dimensions than the radii of a convex curvature on thejoint-facing surface of the first component. Similarly, the radii of aconvex curvature on the opposing joint-facing surface of the secondcomponent can be selected to match or to be slightly smaller in one ormore dimensions than the radii of a concave curvature on thejoint-facing surface of the first component. In this way, contactsurface area can be maximized between articulating convex and concavecurvatures on the respective surfaces of first and second implantcomponents.

The bone-facing surface of the second component can be designed tonegatively-match, at least in part, the shape of articular cartilage,subchondral bone, cortical bone, endosteal bone or bone marrow (e.g.,surface contour, angle, or perimeter shape of a resected or nativebiological structure). It can have any of the features described abovefor the bone-facing surface of the first component, such as having oneor more patient-adapted bone cuts to match one or more predeterminedresection cuts.

Many combinations of first component and second component bone-facingsurfaces and joint-facing surfaces are possible. Table 3 providesillustrative combinations that may be employed.

TABLE 3 Illustrative Combinations of Implant Components 1^(st) 1^(st)2^(nd) 2^(nd) component component 1^(st) component component 2^(nd)bone-facing joint-facing component joint facing bone facing componentsurface surface bone cut(s) surface surface bone cuts Example: Example:Example: Example: Example: Example: Femur Femur Femur Tibia Tibia TibiaAt least one Cartilage Yes Negative-match of 1^(st) At least one Yesbone cut component joint-facing bone cut (opposing cartilage) At leastone Cartilage Yes Negative-match of 1^(st) Subchondral Optional bone cutcomponent joint-facing bone (opposing cartilage) At least one CartilageYes Negative-match of 1^(st) Cartilage Optional bone cut componentjoint-facing (same side, (opposing cartilage) e.g. tibia) At least oneSubchondral Yes Negative-match of 1^(st) At least one Yes bone cut bonecomponent joint-facing bone cut (opposing subchondral bone) At least oneSubchondral Yes Negative-match of 1^(st) Subchondral Optional bone cutbone component joint-facing bone (opposing subchondral bone) At leastone Subchondral Yes Negative-match of 1^(st) Cartilage Optional bone cutbone component joint-facing (same side, (opposing subchondral e.g.tibia) bone) Subchondral Cartilage Optional Negative-match of 1^(st) Atleast one Yes bone component joint-facing bone cut (opposing cartilage)Subchondral Cartilage Optional Negative-match of 1^(st) SubchondralOptional bone component joint-facing bone (opposing cartilage)Subchondral Cartilage Optional Negative-match of 1^(st) CartilageOptional bone component joint-facing (same side, (opposing cartilage)e.g. tibia) Subchondral Subchondral Optional Negative-match of 1^(st) Atleast one Yes bone bone component joint-facing bone cut (opposingsubchondral bone) Subchondral Subchondral Optional Negative-match of1^(st) Subchondral Optional bone bone component joint-facing bone(opposing subchondral bone) Subchondral Subchondral OptionalNegative-match of 1^(st) Cartilage Optional bone bone componentjoint-facing (same side, (opposing subchondral e.g. tibia) bone)Subchondral Standard/ Optional Negative-match of 1^(st) At least one Yesbone Model component joint-facing bone cut standard SubchondralStandard/ Optional Negative-match of 1^(st) Subchondral Optional boneModel component joint-facing bone standard Subchondral Standard/Optional Negative-match of 1^(st) Cartilage Optional bone Modelcomponent joint-facing (same side, standard e.g. tibia) SubchondralSubchondral Optional Non-matching standard At least one Yes bone bonesurface bone cut Subchondral Cartilage Optional Non-matching standard Atleast one Yes bone surface bone cut

2.3 Multi-Component Implants and Implant Systems

The implants and implant systems described herein include any number ofpatient-adapted implant components and any number of non-patient-adaptedimplant components. An illustrative implant or implant system isdepicted in FIGS. 7A-7C. Specifically, FIG. 7A shows a photograph of apatient-adapted knee replacement implant system that includes apatient-specific bicompartmental implant component 700 andpatient-specific unicompartmental implant component 710. Both componentsare patient-specific on both their bone-facing surfaces and on theirjoint-facing surfaces. FIGS. 7B and 7C show x-ray images showing theimplant of FIG. 7A in the coronal plane (FIG. 7B) and the sagittal plane(FIG. 7C).

In certain embodiments, the implants and implant systems describedherein can include a combination of implant components, such as atraditional unicompartmental device with a patient-specificbicompartmental device or a combination of a patient-specificunicompartmental device with standard bicompartmental device. Suchimplant combinations allow for a flexible design of an implant orimplant system that includes both standard and patient-specific featuresand components. This flexibility and level of patient-specificity allowsfor various engineered optimizations, such as retention of alignments,maximization of bone preservation, and/or restoration of normal ornear-normal patient kinematics.

In certain embodiments, an implant component is designed and installedas one or more pieces. For example, FIGS. 8A-8E illustrates a femoralimplant component that can be installed in two pieces.

Embodiments described herein can be applied to partial or total jointreplacement systems. Bone cuts or changes to an implant componentdimension described herein can be applied to a portion of the dimension,or to the entire dimension.

3. Collecting and Modeling Patient-Specific Data

As mentioned above, certain embodiments include implant componentsdesigned and made using patient-specific data that is collectedpreoperatively. The patient-specific data can include points, surfaces,and/or landmarks, collectively referred to herein as “reference points.”In certain embodiments, the reference points can be selected and used toderive a varied or altered surface, such as, without limitation, anideal surface or structure. For example, the reference points can beused to create a model of the patient's relevant biological feature(s)and/or one or more patient-adapted surgical steps, tools, and implantcomponents. For example the reference points can be used to design apatient-adapted implant component having at least one patient-specificor patient-engineered feature, such as a surface, dimension, or otherfeature.

Sets of reference points can be grouped to form reference structuresused to create a model of a joint and/or an implant design. Designedimplant surfaces can be derived from single reference points, triangles,polygons, or more complex surfaces, such as parametric or subdivisionsurfaces, or models of joint material, such as, for example, articularcartilage, subchondral bone, cortical bone, endosteal bone or bonemarrow. Various reference points and reference structures can beselected and manipulated to derive a varied or altered surface, such as,without limitation, an ideal surface or structure.

The reference points can be located on or in the joint that will receivethe patient-specific implant. For example, the reference points caninclude weight-bearing surfaces or locations in or on the joint, acortex in the joint, and/or an endosteal surface of the joint. Thereference points also can include surfaces or locations outside of butrelated to the joint. Specifically, reference points can includesurfaces or locations functionally related to the joint. For example, inembodiments directed to the knee joint, reference points can include oneor more locations ranging from the hip down to the ankle or foot. Thereference points also can include surfaces or locations homologous tothe joint receiving the implant. For example, in embodiments directed toa knee, a hip, or a shoulder joint, reference points can include one ormore surfaces or locations from the contralateral knee, hip, or shoulderjoint.

3.1 Measuring Biological Features

Reference points and/or data for obtaining measurements of a patient'sjoint, for example, relative-position measurements, length or distancemeasurements, curvature measurements, surface contour measurements,thickness measurements (in one location or across a surface), volumemeasurements (filled or empty volume), density measurements, and othermeasurements, can be obtained using any suitable technique. For example,one dimensional, two-dimensional, and/or three-dimensional measurementscan be obtained using data collected from mechanical means, laserdevices, electromagnetic or optical tracking systems, molds, materialsapplied to the articular surface that harden as a negative match of thesurface contour, and/or one or more imaging techniques described aboveand/or known in the art. Data and measurements can be obtainednon-invasively and/or preoperatively. Alternatively, measurements can beobtained intraoperatively, for example, using a probe or other surgicaldevice during surgery.

In certain embodiments, an imaging data collected from the patient, forexample, imaging data from one or more of x-ray imaging, digitaltomosynthesis, cone beam CT, non-spiral or spiral CT, non-isotropic orisotropic MRI, SPECT, PET, ultrasound, laser imaging, photo-acousticimaging, is used to qualitatively and/or quantitatively measure one ormore of a patient's biological features, one or more of normalcartilage, diseased cartilage, a cartilage defect, an area of denudedcartilage, subchondral bone, cortical bone, endosteal bone, bone marrow,a ligament, a ligament attachment or origin, menisci, labrum, a jointcapsule, articular structures, and/or voids or spaces between or withinany of these structures. The qualitatively and/or quantitativelymeasured biological features can include, but are not limited to, one ormore of length, width, height, depth and/or thickness; curvature, forexample, curvature in two dimensions (e.g., curvature in or projectedonto a plane), curvature in three dimensions, and/or a radius or radiiof curvature; shape, for example, two-dimensional shape orthree-dimensional shape; area, for example, surface area and/or surfacecontour; perimeter shape; and/or volume of, for example, the patient'scartilage, bone (subchondral bone, cortical bone, endosteal bone, and/orother bone), ligament, and/or voids or spaces between them.

In certain embodiments, measurements of biological features can includeany one or more of the illustrative measurements identified in Table 4.

TABLE 4 Exemplary patient-specific measurements of biological featuresthat can be used in the creation of a model and/or in the selectionand/or design of an implant component Anatomical feature Exemplarymeasurement Joint-line, joint gap Location relative to proximalreference point Location relative to distal reference point Angle Gapdistance between opposing surfaces in one or more locations Location,angle, and/or distance relative to contralateral joint Soft tissuetension Joint gap distance and/or balance Joint gap differential, e.g.,medial to lateral Medullary cavity Shape in one or more dimensions Shapein one or more locations Diameter of cavity Volume of cavity Subchondralbone Shape in one or more dimensions Shape in one or more locationsThickness in one or more dimensions Thickness in one or more locationsAngle, e.g., resection cut angle Cortical bone Shape in one or moredimensions Shape in one or more locations Thickness in one or moredimensions Thickness in one or more locations Angle, e.g., resection cutangle Endosteal bone Shape in one or more dimensions Shape in one ormore locations Thickness in one or more dimensions Thickness in one ormore locations Angle, e.g., resection cut angle Cartilage Shape in oneor more dimensions Shape in one or more locations Thickness in one ormore dimensions Thickness in one or more locations Angle, e.g.,resection cut angle Intercondylar notch Shape in one or more dimensionsLocation Height in one or more locations Width in one or more locationsDepth in one or more locations Angle, e.g., resection cut angle Medialcondyle 2D and/or 3D shape of a portion or all Height in one or morelocations Length in one or more locations Width in one or more locationsDepth in one or more locations Thickness in one or more locationsCurvature in one or more locations Slope in one or more locations and/ordirections Angle, e.g., resection cut angle Lateral condyle 2D and/or 3Dshape of a portion or all Height in one or more locations Length in oneor more locations Width in one or more locations Depth in one or morelocations Thickness in one or more locations Curvature in one or morelocations Slope in one or more locations and/or directions Angle, e.g.,resection cut angle Trochlea 2D and/or 3D shape of a portion or allHeight in one or more locations Length in one or more locations Width inone or more locations Depth in one or more locations Thickness in one ormore locations Curvature in one or more locations Slope in one or morelocations and/or directions Angle, e.g., resection cut angle Medialtrochlea 2D and/or 3D shape of a portion or all Height in one or morelocations Length in one or more locations Width in one or more locationsDepth in one or more locations Thickness in one or more locationsCurvature in one or more locations Slope in one or more locations and/ordirections Angle, e.g., resection cut angle Central trochlea 2D and/or3D shape of a portion or all Height in one or more locations Length inone or more locations Width in one or more locations Depth in one ormore locations Thickness in one or more locations Curvature in one ormore locations Slope in one or more locations and/or directions Angle,e.g., resection cut angle Lateral trochlea 2D and/or 3D shape of aportion or all Height in one or more locations Length in one or morelocations Width in one or more locations Depth in one or more locationsThickness in one or more locations Curvature in one or more locationsSlope in one or more locations and/or directions Angle, e.g., resectioncut angle Entire tibia 2D and/or 3D shape of a portion or all Height inone or more locations Length in one or more locations Width in one ormore locations Depth in one or more locations Thickness in one or morelocations Curvature in one or more locations Slope in one or morelocations and/or directions Angle, e.g., resection cut angle Axes, e.g.,A-P and/or M-L axes Osteophytes Plateau slope(s), e.g., relative slopesmedial and lateral Plateau heights(s), e.g., relative heights medial andlateral Bearing surface radii, e.g., e.g., relative radii medial andlateral Perimeter profile Medial tibia 2D and/or 3D shape of a portionor all Height in one or more locations Length in one or more locationsWidth in one or more locations Depth in one or more locations Thicknessor height in one or more locations Curvature in one or more locationsSlope in one or more locations and/or directions Angle, e.g., resectioncut angle Perimeter profile Lateral tibia 2D and/or 3D shape of aportion or all Height in one or more locations Length in one or morelocations Width in one or more locations Depth in one or more locationsThickness/height in one or more locations Curvature in one or morelocations Slope in one or more locations and/or directions Angle, e.g.,resection cut angle Perimeter profile Entire patella 2D and/or 3D shapeof a portion or all Height in one or more locations Length in one ormore locations Width in one or more locations Depth in one or morelocations Thickness in one or more locations Curvature in one or morelocations Slope in one or more locations and/or directions Perimeterprofile Angle, e.g., resection cut angle Medial patella 2D and/or 3Dshape of a portion or all Height in one or more locations Length in oneor more locations Width in one or more locations Depth in one or morelocations Thickness in one or more locations Curvature in one or morelocations Slope in one or more locations and/or directions Angle, e.g.,resection cut angle Central patella 2D and/or 3D shape of a portion orall Height in one or more locations Length in one or more locationsWidth in one or more locations Depth in one or more locations Thicknessin one or more locations Curvature in one or more locations Slope in oneor more locations and/or directions Angle, e.g., resection cut angleLateral patella 2D and/or 3D shape of a portion or all Height in one ormore locations Length in one or more locations Width in one or morelocations Depth in one or more locations Thickness in one or morelocations Curvature in one or more locations Slope in one or morelocations and/or directions Angle, e.g., resection cut angle Femoralhead 2D and/or 3D shape of a portion or all Height in one or morelocations Length in one or more locations Width in one or more locationsDepth in one or more locations Thickness in one or more locationsCurvature in one or more locations Slope in one or more locations and/ordirections Angle, e.g., resection cut angle Acetabulum 2D and/or 3Dshape of a portion or all Height in one or more locations Length in oneor more locations Width in one or more locations Depth in one or morelocations Thickness in one or more locations Curvature in one or morelocations Slope in one or more locations and/or directions Angle, e.g.,resection cut angle Glenoid 2D and/or 3D shape of a portion or allHeight in one or more locations Length in one or more locations Width inone or more locations Depth in one or more locations Thickness in one ormore locations Curvature in one or more locations Slope in one or morelocations and/or directions Angle, e.g., resection cut angle Humeralhead 2D and/or 3D shape of a portion or all Height in one or morelocations Length in one or more locations Width in one or more locationsDepth in one or more locations Thickness in one or more locationsCurvature in one or more locations Slope in one or more locations and/ordirections Angle, e.g., resection cut angle Ankle joint 2D and/or 3Dshape of a portion or all Height in one or more locations Length in oneor more locations Width in one or more locations Depth in one or morelocations Thickness in one or more locations Curvature in one or morelocations Slope in one or more locations and/or directions Angle, e.g.,resection cut angle Elbow 2D and/or 3D shape of a portion or all Heightin one or more locations Length in one or more locations Width in one ormore locations Depth in one or more locations Thickness in one or morelocations Curvature in one or more locations Slope in one or morelocations and/or directions Angle, e.g., resection cut angle Wrist 2Dand/or 3D shape of a portion or all Height in one or more locationsLength in one or more locations Width in one or more locations Depth inone or more locations Thickness in one or more locations Curvature inone or more locations Slope in one or more locations and/or directionsAngle, e.g., resection cut angle Hand 2D and/or 3D shape of a portion orall Height in one or more locations Length in one or more locationsWidth in one or more locations Depth in one or more locations Thicknessin one or more locations Curvature in one or more locations Slope in oneor more locations and/or directions Angle, e.g., resection cut angleFinger 2D and/or 3D shape of a portion or all Height in one or morelocations Length in one or more locations Width in one or more locationsDepth in one or more locations Thickness in one or more locationsCurvature in one or more locations Slope in one or more locations and/ordirections Angle Spine 2D and/or 3D shape of a portion or all Height inone or more locations Length in one or more locations Width in one ormore locations Depth in one or more locations Thickness in one or morelocations Curvature in one or more locations Slope in one or morelocations and/or directions Angle, e.g., resection cut angle Spinalfacet joint 2D and/or 3D shape of a portion or all Height in one or morelocations Length in one or more locations Width in one or more locationsDepth in one or more locations Thickness in one or more locationsCurvature in one or more locations Slope in one or more locations and/ordirections Angle, e.g., resection cut angle

Depending on the clinical application, a single or any combination orall of the measurements described in Table 4 and/or known in the art canbe used. Additional patient-specific measurements and information thatbe used in the evaluation can include, for example, joint kinematicmeasurements, bone density measurements, bone porosity measurements,identification of damaged or deformed tissues or structures, and patientinformation, such as patient age, weight, gender, ethnicity, activitylevel, and overall health status.

The patient-specific measurements selected for the evaluation then canbe used to select (e.g., from a library), to design, or to select anddesign an implant component having one or more measurementscorresponding to or derived from the one or more of the assessedpatient-specific measurements. For example, the implant component caninclude one or more patient-specific measurements and/or one or morepatient-engineered measurements. Optionally, one or morepatient-specific models, one or more patient-adapted surgical steps,and/or one or more patient-adapted surgical guide tools also can beselected and/or designed to include one or more measurementscorresponding to or derived from the one or more of thesepatient-specific measurements.

3.2 Generating a Model of a Joint

In certain embodiments, one or more models of at least a portion of apatient's joint can be generated. Specifically, the patient-specificdata and/or measurements described above can be used to generate a modelthat includes at least a portion of the patient's joint. Optionally, oneor more patient-engineered resection cuts, one or more drill holes, oneor more patient-adapted guide tools, and/or one or more patient-adaptedimplant components can be included in a model. In certain embodiments, amodel of at least part of a patient's joint can be used to directlygenerate a patient-engineered resection cut strategy, a patient-adaptedguide tool design, and/or a patient-adapted implant component design fora surgical procedure (i.e., without the model itself including one ormore resection cuts, one or more drill holes, one or more guide tools,and/or one or more implant components). In certain embodiments, themodel that includes at least a portion of the patient's joint also caninclude or display, as part of the model, one or more resection cuts,one or more drill holes, (e.g., on a model of the patient's femur), oneor more guide tools, and/or one or more implant components that havebeen designed for the particular patient using the model. Moreover, oneor more resection cuts, one or more drill holes, one or more guidetools, and/or one or more implant components can be modeled and selectedand/or designed separate from a model of a particular patient'sbiological feature.

Various methods can be used to generate a model. As illustrated in FIG.9A, in certain embodiments the method of generating a model of apatient's joint (and/or a resection cut, drill hole, guide tool, and/orimplant component) can include one or more of the steps of obtainingimage data of a patient's biological structure 910; segmenting the imagedata 930; combining the segmented data 940; and presenting the data aspart of a model 950.

Image data can be obtained 910 from near or within the patient'sbiological structure of interest. For example, pixel or voxel data fromone or more radiographic or tomographic images of a patient's joint canbe obtained, for example, using computed or magnetic resonancetomography. In this or a subsequent step, one or more of the pixels orvoxels can be converted into one or a set of values. For example, asingle pixel/voxel or a group of pixel/voxels can be converted tocoordinate values, e.g., a point in a 2D or 3D coordinate system. Theset of values also can include a value corresponding to the pixel/voxelintensity or relative grayscale color. Moreover, the set of values caninclude information about neighboring pixels or voxels, for example,information corresponding to relative intensity or grayscale color andor information corresponding to relative position.

Then, the image data can be segmented 930 to identify those datacorresponding to a particular biological feature of interest.Optionally, the segmented data can be combined. For example, in a singleimage segmented and selected reference points (e.g., derived from pixelsor voxels) and/or other data can be combined to create a linerepresenting the surface outline of a biological structure. Moreover,the segmented and selected data from multiple images can be combined tocreate a 3D representation of the biological structure. Alternatively,the images can be combined to form a 3D data set, from which the 3Drepresentation of the biological structure can be derived directly usinga 3D segmentation technique, for example an active surface or activeshape model algorithm or other model based or surface fitting algorithm.

Optionally, the 3D representation of the biological structure can begenerated or manipulated, for example, smoothed or corrected, forexample, by employing a 3D polygon surface, a subdivision surface orparametric surface, for example, a non-uniform rational B-spline (NURBS)surface. For a description of various parametric surface representationssee, for example Foley, J. D. et al., Computer Graphics: Principles andPractice in C; Addison-Wesley, 2nd edition, 1995). Various methods areavailable for creating a parametric surface. For example, the 3Drepresentation can be converted directly into a parametric surface, forexample, by connecting data points to create a surface of polygons andapplying rules for polygon curvatures, surface curvatures, and otherfeatures. Alternatively, a parametric surface can be best-fit to the 3Drepresentation, for example, using publicly available software such asGeomagic® software (Research Triangle Park, N.C.).

Then, the data can be presented as part of a model 950, for example, apatient-specific virtual model that includes the biological feature ofinterest. Optionally, the data associated with one or more biologicalfeatures can be transferred to one or more resection cuts, drill holes,guide tools, and/or implant components, which also can be included aspart of the same model or in a different model. The virtual model(s) canbe used to generate one or more patient-adapted guide tools and/orimplant components for surgical use, for example, using computer-aideddesign (CAD) software and/or one or more of the several manufacturingtechniques described below, optionally in conjunction withcomputer-aided manufacturing (CAM) software.

As will be appreciated by those of skill in the art, one or more ofthese steps 910, 930, 940, 950 can be repeated 911, 931, 941, 951 asoften as desired to achieve the desired result. Moreover, the steps canbe repeated reiteratively 932, 933, 934. Moreover, the practitioner canproceed directly 933 from the step of segmenting image data 930 topresenting the data as part of a model 950. Data, models and/or anyrelated guide tools or implant components can be collected in one ormore libraries for subsequent use for the same patient or for adifferent patient (e.g., a different patient with similar data).

3.3 Modeling and Addressing Joint Defects

In certain embodiments, the reference points and/or measurementsdescribed above can be processed using mathematical functions to derivevirtual, corrected features, which may represent a restored, ideal ordesired feature from which a patient-adapted implant component can bedesigned. For example, one or more features, such as surfaces ordimensions of a biological structure can be modeled, altered, added to,changed, deformed, eliminated, corrected and/or otherwise manipulated(collectively referred to herein as “variation” of an existing surfaceor structure within the joint).

Variation of the joint or portions of the joint can include, withoutlimitation, variation of one or more external surfaces, internalsurfaces, joint-facing surfaces, uncut surfaces, cut surfaces, alteredsurfaces, and/or partial surfaces as well as osteophytes, subchondralcysts, geodes or areas of eburnation, joint flattening, contourirregularity, and loss of normal shape. The surface or structure can beor reflect any surface or structure in the joint, including, withoutlimitation, bone surfaces, ridges, plateaus, cartilage surfaces,ligament surfaces, or other surfaces or structures. The surface orstructure derived can be an approximation of a healthy joint surface orstructure or can be another variation. The surface or structure can bemade to include pathological alterations of the joint. The surface orstructure also can be made whereby the pathological joint changes arevirtually removed in whole or in part.

Once one or more reference points, measurements, structures, surfaces,models, or combinations thereof have been selected or derived, theresultant shape can be varied, deformed or corrected. In certainembodiments, the variation can be used to select and/or design animplant component having an ideal or optimized feature or shape, e.g.,corresponding to the deformed or corrected joint feature or shape. Forexample, in one application of this embodiment, the ideal or optimizedimplant shape reflects the shape of the patient's joint before he or shedeveloped arthritis.

Alternatively or in addition, the variation can be used to select and/ordesign a patient-adapted surgical procedure to address the deformity orabnormality. For example, the variation can include surgical alterationsto the joint, such as virtual resection cuts, virtua; drill holes,virtual removal of osteophytes, and/or virtual building of structuralsupport in the joint deemed necessary or beneficial to a desired finaloutcome for a patient.

Corrections can be used to address osteophytes, subchondral voids, andother patient-specific defects or abnormalities. In the case ofosteophytes, a design for the bone-facing surface of an implantcomponent or guide tool can be selected and/or designed after theosteophyte has been virtually removed. Alternatively, the osteophyte canbe integrated into the shape of the bone-facing surface of the implantcomponent or guide tool. FIGS. 10A-10D are exemplary drawings of an endof a femur 1010 having an osteophyte 1020. In the selection and/ordesign of an implant component for a particular patient, an image ormodel of the patient's bone that includes the osteophyte can betransformed such that the osteophyte 1020 is virtually removed, as shownin FIG. 10B at removed osteophyte 1030, to produce, as shown in FIG.10C, an implant component 1040 based on a smooth surface at the end offemur 1010. Alternatively, as shown in FIG. 10D, an implant component1050 can be selected and/or designed to conform to the shape of theosteophyte 1020. In the case of building additional or improvedstructure, additional features of the implant component then can bederived after bone-facing surface correction is modeled. Optionally, asurgical strategy and/or one or more guide tools can be selected and/ordesigned to reflect the correction and correspond to the implantcomponent.

Similarly, to address a subchondral void, a selection and/or design forthe bone-facing surface of an implant component can be derived after thevoid has been virtually removed (e.g., filled). Alternatively, thesubchondral void can be integrated into the shape of the bone-facingsurface of the implant component. FIGS. 11A-11D are exemplary drawingsof an end of a femur 1110 having a subchondral void 1120. Duringdevelopment of an implant, an image or model of the patient's bone thatincludes the void can be transformed such that the void 1120 isvirtually removed, as shown in FIG. 11B at removed void 1130, toproduce, as shown in FIG. 11C, an implant component 1140 based on asmooth surface at the end of femur 1110. Alternatively, implant 1110 canbe selected and/or designed to conform to the shape of void 1120, asshown in FIG. 11D. Note that, while virtually conforming to void 1120,implant 1150 may not practically be able to be inserted into the void.Therefore, in an certain embodiments, the implant may only partiallyprotrude into a void in the bone. Optionally, a surgical strategy and/orone or more guide tools can be selected and/or designed to reflect thecorrection and correspond to the implant component.

In addition to osteophytes and subchondral voids, the methods, surgicalstrategies, guide tools, and implant components described herein can beused to address various other patient-specific joint defects orphenomena. In certain embodiments, correction can include the virtualremoval of tissue, for example, to address an articular defect, toremove subchondral cysts, and/or to remove diseased or damaged tissue(e.g., cartilage, bone, or other types of tissue), such asosteochondritic tissue, necrotic tissue, and/or torn tissue. In suchembodiments, the correction can include the virtual removal of thetissue (e.g., the tissue corresponding to the defect, cyst, disease, ordamage) and the bone-facing surface of the implant component can bederived after the tissue has been virtually removed. In certainembodiments, the implant component can be selected and/or designed toinclude a thickness or other features that substantially matches theremoved tissue and/or optimizes one or more parameters of the joint.Optionally, a surgical strategy and/or one or more guide tools can beselected and/or designed to reflect the correction and correspond to theimplant component.

In certain embodiments, a correction can include the virtual addition oftissue or material, for example, to address an articular defect, loss ofligament stability, and/or a bone stock deficiency, such as a flattenedarticular surface that should be round. In certain embodiments, theadditional material may be virtually added (and optionally then added insurgery) using filler materials such as bone cement, bone graftmaterial, and/or other bone fillers. Alternatively or in addition, theadditional material may be virtually added as part of the implantcomponent, for example, by using a bone-facing surface and/or componentthickness that match the correction or by otherwise integrating thecorrection into the shape of the implant component. Then, thejoint-facing and/or other features of the implant can be derived. Thiscorrection can be designed to re-establish a near normal shape for thepatient. Alternatively, the correction can be designed to establish astandardized shape or surface for the patient.

In certain embodiments, the patient's abnormal or flattened articularsurface can be integrated into the shape of the implant component, forexample, the bone-facing surface of the implant component can bedesigned to substantially negatively-match the abnormal or flattenedsurface, at least in part, and the thickness of the implant can bedesigned to establish the patient's healthy or an optimum position ofthe patient's structure in the joint. Moreover, the joint-facing surfaceof the implant component also can be designed to re-establish a nearnormal anatomic shape reflecting, for example, at least in part theshape of normal cartilage or subchondral bone. Alternatively, it can bedesigned to establish a standardized shape.

In certain embodiments, models can be generated to show defects ofinterest in a patient's joint. For example, a model or set of models ofa patient's joint can be generated showing defects of interest and,optionally, another model or set of models can be generated showing nodefects (e.g., as defect and reference, or before and after models).Alternatively, or in addition, the same or additional models can begenerated with and/or without resection cuts, guide tools, and/orimplant components positioned in the model. Moreover, the same oradditional models can be generated to show defects of interest thatinterfere with one or more resection cuts, guide tools, and/or implantcomponents. Such models, showing defects of interest, resection cuts,guide tools, implant components, and/or interfering defects of interest,can be particularly useful as a reference or guide to a surgeon orclinician prior to and/or during surgery, for example, in identifyingproper placement of a guide tool or implant component at one or moresteps in a surgery, and/or in identifying features of a patient'sanatomy that he or she may want to alter during one or more steps in asurgery. Accordingly, such models that provide, for example,patient-specific renderings of implant assemblies and defects ofinterest (e.g., osteophyte structures) together with bone models, areuseful in aiding surgeons and clinicians in surgery planning and/orduring surgery.

In certain embodiments, a model or set of models of a patient'sbiological structure are obtained and/or generated to show one or moredefects of interest, one or more resection cuts, one or more guidetools, one or more implant components, and/or a combination of any ofthese. For models that include defects of interest, the defects can becategorized and differentiated into various groups and displayed on themodel or set of models in any way that conveys the appropriateinformation to a surgeon or clinician. For example, two or more defectscan be differentiated into categories based on defect type, defectlocation, severity of the defect, potential interference with a guidetool or implant component, and/or any one or more other usefulcategories.

In certain embodiments, one or more additional models or set of modelsof the patient's biological structure also can be generated and conveyedto the surgeon or clinician to show an additional presence, or absence,of one or more defects of interest, one or more resection cuts, one ormore guide tools, and/or one or more implant components, or anycombination of these. FIGS. 12A and 12B illustrate models for oneparticular patient receiving a single compartment knee implant havingboth femoral and tibial implant components. In a first set of models,illustrated in FIG. 12A, the top panel shows two perspectives of apatient's distal femur and the bottom panel shows two images of thepatient's proximal tibia, without (left image) and with (right image) apatient-adapted guide tool. In both the top and bottom panels, defects,osteophytes in this example, are categorized and differentiated into twocolors, beige and red. The light-colored osteophytes 1210 depictosteophytes that do not interfere with placement of the guide tools orimplant components. The dark-colored osteophytes 1220 depict osteophytesthat will interfere with placement of a guide tool or an implantcomponent. Accordingly, the categorization of the osteophytes serve as aguide or reference to the surgeon or clinician in determining whichosteophytes should be removed prior to placement of the guide tools orimplant components.

In a second set of models, illustrated in FIG. 12B, the top panel showstwo images of a patient's distal femur with a patient-adapted guide tool(left image) and with a patient-adapted unicompartmental femoral implantcomponent (right image). The bottom panel shows two images of thepatient's proximal tibia, with a patient-adapted guide tool (left image)and with a patient-adapted unicompartmental tibial implant component(right image). The images in this figure show no osteophytes. Instead,these images show how each guide tool and implant component engages thepatient's biological structure. In addition, the images showing theguide tools also show corresponding resection planes 1230 and thepatient's tibial mechanical axis 1240. Accordingly, these images canserve as a guide or reference to the surgeon or clinician in planningand/or determining the surgical placement of the guide tools, implantcomponents, and related resection cuts.

FIGS. 13A and 13B illustrate models for a different patient receiving abicompartmental knee implant having both femoral and tibial implantcomponents. The features in FIGS. 13A and 13B are similar to thosedescribed above for FIGS. 12A and 12B. In comparing the models for thetwo different individuals, it is clear that the individual receiving theunicompartmental knee implant (FIGS. 12A and 12B) has substantially moreosteophyte coverage than the individual receiving the bicompartmentalknee implant (FIGS. 13A and 13B).

Computer software programs to generate models of patient-specificrenderings of implant assembly and defects (e.g., osteophytestructures), together with bone models, to aid in surgery planning canbe developed using various publicly available programming environmentsand languages, for example, Matlab 7.3 and Matlab Compiler 4.5, C++ orJava. In certain embodiments, the computer software program can have auser interface that includes one or more of the components identified inFIG. 14. Alternatively, one or more off-the-shelf applications can beused to generate the models, such as SolidWorks, Rhinoceros, 3D Sliceror Amira.

An illustrative flow chart of the high level processes of an exemplarycomputer software program is shown in FIG. 15. Briefly, a data pathassociated with one or more patient folders that include data files, forexample, patient-specific CT images, solid models, and segmentationimages, is selected. The data files associated with the data path can bechecked, for example, using file filters, to confirm that all data filesare present. For example, in generating models for a knee implant, adata path can confirm the presence of one, several, or all coronal CTdata files, sagittal CT data files, a femoral solid model data file, atibial solid model data file, a femoral guide tool model, a tibial guidetool model, a femoral coronal segmentation model, a femoral sagittalsegmentation model, a tibial coronal segmentation model, and a tibialsagittal segmentation model. If the filter check identifies a missingfile, the user can be notified. In certain instances, for example, if atibial or femoral guide tool model file is unavailable, the user mayelect to continue the process without certain steps, for example,without guide tool—defect (e.g., osteophyte) interference analysis.

Next, a patient-specific bone-surface model is obtained and/or rendered.The bone surface model provides basic patient-specific features of thepatient's biological structure and serves as a reference for comparisonagainst a model or value that includes the defect(s) of interest. As anillustrative example, previously generated patient-specific files, forexample, STL files exported from “SOLID” IGES files in SolidWorks, canbe loaded, for example, as triangulation points with sequence indicesand normal vectors. The triangles then can be rendered (e.g., usingMatlab TRISURF function) to supply or generate the bone-surface model.The bone surface model can include corrections of defects, such asosteophytes removed from the bone. In a similar fashion, one or moreguide tool models can be obtained and/or rendered.

Next, a patient-specific model or values of the patient's biologicalfeature that include the defect of interest can be obtained and/orrendered. For example, patient-specific defects, such as osteophytes,can be identified from analysis of the patient's segmentation images andcorresponding CT scan images. The transformation matrix of scannercoordinate space to image matrix space can be calculated from imageslice positions (e.g., the first and last image slice positions). Then,patient-specific segmentation images for the corresponding scandirection can be assessed, along with CT image slices that correspond tothe loaded segmentation images. Images can be processed slice by sliceand, using selected threshold values (e.g., intensity thresholds,Hounsfield unit thresholds, or neighboring pixel/voxel valuethresholds), pixels and/or voxels corresponding to the defects ofinterest (e.g., osteophytes) can be identified. The identified voxelscan provide a binary bone surface volume that includes the defects ofinterest as part of the surface of the patient's biological structure.Various masks can be employed to mask out features that are not ofinterest, for example, an adjacent biological surface. In someinstances, masking can generate apparent unattached portions of anosteophyte defect, for example, when a mask covers a portion of anosteophyte extension.

Next, the defects of interest are isolated by comparing the model thatdoes not include the defects of interest (e.g., bone-surface model) withthe model or value that does include the defects of interest (e.g., thebinary bone surface volume). For example, the triangulation points ofthe bone surface model can be transformed onto an image volume space toobtain a binary representation of the model. This volume binary can bedilated and thinned to obtain a binary bone model. The binary bone modelthen can serve as a mask to the binary bone surface volume to identifydefect volume separate from the binary bone surface volume. For example,for osteophyte detection, the osteophyte volume (e.g., osteophyte binaryvolume), as well as the osteophyte position and attachment surface area,can be distinguished from the patient's biological structure using thiscomparative analysis. Various thresholds and filters can be applied toremove noise and/or enhance defect detection in this step. For example,structures that have less than a minimum voxel volume (e.g., less than100 voxels) can be removed. Alternatively, or in addition, rules can beadded to “reattach” any portion of an osteophyte defect that appearsunattached, e.g., due to a masking step.

In an alternative approach, surface data can be used instead of voxel orvolume data when comparing the bone surface model with corrected defectsand the patient's actual bone surface. The bone surface model, forexample, can be loaded as a mesh surface (e.g. in an STL file) or aparametric surface (e.g. in an IGES file) without conversion tovolumetric voxel data. The patient's natural bone surface can be derivedfrom the medical image data (e.g. CT data) using, for example, amarching cubes or isosurface algorithm, resulting in a second surfacedata set. The bone surface model and the natural bone surface can becompared, for example, by calculating intersection between the twosurfaces.

Next, optionally, the models can be used to detect interference betweenany defect volume and the placement of one or more guide tools and/orimplant components. For example, guide tool model triangulation pointscan be transformed onto an image volume space to obtain a binaryrepresentation of the guide tool. The binary structure then can bemanipulated (e.g., dilated and eroded using voxel balls having pre-setdiameters) to obtain a solid field mask. The solid field mask can becompared against the defect volume, for example, the osteophyte binaryvolume, to identify interfering defect volume, for example, interferingosteophyte binary volume. In this way, interfering defect volume andnon-interfering defect volume can be determined (e.g., using MatlabISOSURFACE function), for example, using representative colors or someother distinguishing features in a model. See, e.g., FIGS. 12A and 13A.The resulting model image can be rendered on a virtual rendering canvas(e.g., using Matlab GETFRAME function) and saved onto acomputer-readable medium.

Finally, optionally, as exemplified by FIGS. 12A-B and 13A-B, one ormore combinations of model features can be combined into one or modelsor sets of models that convey desired information to the surgeon orclinician. For example, patient-specific bone models can be combinedwith any number of defects or defect types, any number of resectioncuts, any number of drill holes, any number of axes, any number of guidetools, and/or any number of implant components to convey as muchinformation as desired to the surgeon or clinician. The patient-specificbone model can model any biological structure, for example, any one ormore (or portion of) a femoral head and/or an acetabulum; a distalfemur, one or both femoral condyle(s), and/or a tibial plateau; atrochlea and/or a patella; a glenoid and/or a humeral head; a talar domeand/or a tibial plafond; a distal humerus, a radial head, and/or anulna; and a radius and/or a scaphoid. Defects that can be combined witha patient-specific bone model can include, for example, osteophytes,voids, subchondral cysts, articular shape defects (e.g., rounded orflattened articular surfaces or surface portions), varus or valgusdeformities, or any other deformities known to those in the art.

The models can include virtual corrections reflecting a surgical plan,such as one or more of removed osteophytes, cut planes, drill holes,realignments of mechanical or anatomical axes. The models can includecomparison views demonstrating the anatomical situation before and afterapplying the planned correction. The individual steps of the surgicalplan can also be illustrated in a series of step-by-step images whereineach image shows a different step of the surgical procedure.

The models can be presented to the surgeon as a printed or digital setof images. In another embodiment, the models are transmitted to thesurgeon as a digital file, which the surgeon can display on a localcomputer. The digital file can contain image renderings of the models.Alternatively, the models can be displayed in an animation or video. Themodels can also be presented as a 3D model that is interactivelyrendered on the surgeon's computer. The models can, for example, berotated to be viewed from different angles. Different components of themodels, such as bone surfaces, defects, resection cuts, axes, guidetools or implants, can be turned on and off collectively or individuallyto illustrate or simulate the individual patient's surgical plan. The 3Dmodel can be transmitted to the surgeon in a variety of formats, forexample in Adobe 3D PDF or as a SolidWorks eDrawing.

3.4 Modeling Proper Limb Alignment

Proper joint and limb function depend on correct limb alignment. Forexample, in repairing a knee joint with one or more knee implantcomponents, optimal functioning of the new knee depends on the correctalignment of the anatomical and/or mechanical axes of the lowerextremity. Accordingly, an important consideration in designing and/orreplacing a natural joint with one or more implant components is properlimb alignment or, when the malfunctioning joint contributes to amisalignment, proper realignment of the limb.

Certain embodiments described herein include collecting and using datafrom imaging tests to virtually determine in one or more planes one ormore of an anatomic axis and a mechanical axis and the relatedmisalignment of a patient's limb. The misalignment of a limb jointrelative to the axis can identify the degree of deformity, for example,varus or valgus deformity in the coronal plane or genu antecurvatum orrecurvatum deformity in the sagittal plane. Then, one or more of thepatient-specific implant components and/or the implant procedure steps,such as bone resection, can be designed to help correct themisalignment.

The imaging tests that can be used to virtually determine a patient'saxis and misalignment can include one or more of such as x-ray imaging,digital tomosynthesis, cone beam CT, non-spiral or spiral CT,non-isotropic or isotropic MRI, SPECT, PET, ultrasound, laser imaging,and photoacoustic imaging, including studies utilizing contrast agents.Data from these tests can be used to determine anatomic reference pointsor limb alignment, including alignment angles within the same andbetween different joints or to simulate normal limb alignment. Anyanatomic features related to the misalignment can be selected andimaged. For example, in certain embodiments, such as for a knee or hipimplant, the imaging test can include data from at least one of, orseveral of, a hip joint, knee joint and ankle joint.

The imaging test can be obtained in lying, prone, supine or standingposition. The imaging test can include only the target joint, or boththe target joint and also selected data through one or more adjoiningjoints.

Using the image data, one or more mechanical or anatomical axes, angles,planes or combinations thereof can be determined. In certainembodiments, such axes, angles, and/or planes can include, or be derivedfrom, one or more of a Whiteside's line, Blumensaat's line,transepicondylar line, femoral shaft axis, femoral neck axis, acetabularangle, lines tangent to the superior and inferior acetabular margin,lines tangent to the anterior or posterior acetabular margin, femoralshaft axis, tibial shaft axis, transmalleolar axis, posterior condylarline, tangent(s) to the trochlea of the knee joint, tangents to themedial or lateral patellar facet, lines tangent or perpendicular to themedial and lateral posterior condyles, lines tangent or perpendicular toa central weight-bearing zone of the medial and lateral femoralcondyles, lines transecting the medial and lateral posterior condyles,for example through their respective centerpoints, lines tangent orperpendicular to the tibial tuberosity, lines vertical or at an angle toany of the aforementioned lines, and/or lines tangent to or intersectingthe cortical bone of any bone adjacent to or enclosed in a joint.Moreover, estimating a mechanical axis, an angle, or plane also can beperformed using image data obtained through two or more joints, such asthe knee and ankle joint, for example, by using the femoral shaft axisand a centerpoint or other point in the ankle, such as a point betweenthe malleoli.

As one example, if surgery of the knee or hip is contemplated, theimaging test can include acquiring data through at least one of, orseveral of, a hip joint, knee joint or ankle joint. As another example,if surgery of the knee joint is contemplated, a mechanical axis can bedetermined. For example, the centerpoint of the hip knee and ankle canbe determined. By connecting the centerpoint of the hip with that of theankle, a mechanical axis can be determined in the coronal plane. Theposition of the knee relative to said mechanical axis can be areflection of the degree of varus or valgus deformity. The samedeterminations can be made in the sagittal plane, for example todetermine the degree of genu antecurvatum or recurvatum. Similarly, anyof these determinations can be made in any other desired planes, in twoor three dimensions.

Exemplary methods for virtually aligning a patient's lower extremity aredescribed below in Example 9. In particular, Example 9 illustratesmethods for determining a patient's tibial mechanical axis, femoralmechanical axis, and the sagittal and coronal planes for each axis.However, any current and future method for determining limb alignmentand simulating normal knee alignment can be used.

Once the proper alignment of the patient's extremity has been determinedvirtually, one or more surgical steps (e.g., resection cuts), surgicaltools (e.g., tools to guide the resection cuts), and/or implantcomponents (e.g., components having variable thicknesses to addressmisalignment).

3.5 Modeling Articular Cartilage

Cartilage loss in one compartment can lead to progressive jointdeformity. For example, cartilage loss in a medial compartment of theknee can lead to varus deformity. In certain embodiments, cartilage losscan be estimated in the affected compartments. The estimation ofcartilage loss can be done using an ultrasound MRI or CT scan or otherimaging modality, optionally with intravenous or intra-articularcontrast. The estimation of cartilage loss can be as simple as measuringor estimating the amount of joint space loss seen on x-rays. For thelatter, typically standing x-rays are preferred. If cartilage loss ismeasured from x-rays using joint space loss, cartilage loss on one ortwo opposing articular surfaces can be estimated by, for example,dividing the measured or estimated joint space loss by two to reflectthe cartilage loss on one articular surface. Other ratios orcalculations are applicable depending on the joint or the locationwithin the joint. Subsequently, a normal cartilage thickness can bevirtually established on one or more articular surfaces by simulatingnormal cartilage thickness. In this manner, a normal or near normalcartilage surface can be derived. Normal cartilage thickness can bevirtually simulated using a computer, for example, based on computermodels, for example using the thickness of adjacent normal cartilage,cartilage in a contralateral joint, or other anatomic informationincluding subchondral bone shape or other articular geometries.Cartilage models and estimates of cartilage thickness can also bederived from anatomic reference databases that can be matched, forexample, to a patient's weight, sex, height, race, gender, or articulargeometry(ies).

In certain embodiments, a patient's limb alignment can be virtuallycorrected by realigning the knee after establishing a normal cartilagethickness or shape in the affected compartment by moving the jointbodies, for example, femur and tibia, so that the opposing cartilagesurfaces including any augmented or derived or virtual cartilage surfacetouch each other, typically in the preferred contact areas. Thesecontact areas can be simulated for various degrees of flexion orextension.

4. Parameters for Selecting and/or Designing a Patient-Adapted Implant

The patient-adapted implants (e.g., implants having one or morepatient-specific and/or patient-engineered features) of certainembodiments can be designed based on patient-specific data to optimizeone or more parameters including, but not limited to: (1) deformitycorrection and limb alignment (2) maximum preservation of bone,cartilage, or ligaments, (3) preservation and/or optimization offeatures of the patient's biology, such as trochlea and trochlear shape,(4) restoration and/or optimization of joint kinematics, and (5)restoration or optimization of joint-line location and/or joint gapwidth. Various features of an implant component that can be designed orengineered based on the patient-specific data to help meet any number ofuser-defined thresholds for these parameters. The features of an implantthat can be designed and/or engineered patient-specifically can include,but are not limited to, (a) implant shape, external and internal, (b)implant size, (c) and implant thickness.

There are several advantages that a patient-specific implant designedand/or engineered to meet or improve one of more of these parameters canhave over a traditional implant. These advantages can include, forexample: improved mechanical stability of the extremity; opportunity fora pre-primary or additional revision implant; improved fit with existingor modified biological features; improved motion and kinematics, andother advantages.

4.1 Deformity Correction and Optimizing Limb Alignment

Information regarding the misalignment and the proper mechanicalalignment of a patient's limb, for example, as illustrated in Example 9,can be used to preoperatively design and/or select one or more featuresof a joint implant and/or implant procedure. For example, based on thedifference between the patient's misalignment and the proper mechanicalaxis, a knee implant and implant procedure can be designed and/orselected preoperatively to include implant and/or resection dimensionsthat substantially realign the patient's limb to correct or improve apatient's alignment deformity. In addition, the process can includeselecting and/or designing one or more surgical tools (e.g., guide toolsor cutting jigs) to direct the clinician in resectioning the patient'sbone in accordance with the preoperatively designed and/or selectedresection dimensions.

In certain embodiments, the degree of deformity correction that isnecessary to establish a desired limb alignment is calculated based oninformation from the alignment of a virtual model of a patient's limb.The virtual model can be generated from patient-specific data, such 2Dand/or 3D imaging data of the patient's limb. The deformity correctioncan correct varus or valgus alignment or antecurvatum or recurvatumalignment. In a preferred embodiment, the desired deformity correctionreturns the leg to normal alignment, for example, a zero degreebiomechanical axis in the coronal plane and absence of genu antecurvatumand recurvatum in the sagittal plane.

The preoperatively designed and/or selected implant or implantcomponent, resection dimension(s), and/or cutting jig(s) can be employedto correct a patient's alignment deformity in a single plane, forexample, in the coronal plane or in the sagittal plane, in multipleplanes, for example, in the coronal and sagittal planes, and/or in threedimensions. For example, Example 9 describes a virtual model of apatient's misaligned lower limb and virtually corrected limb. Inparticular, the patient's lower limb is misaligned in the coronal plane,for example, a valgus or varus deformity. The deformity correction canbe achieved by designing and/or selecting one or more of a resectiondimension, an implant component thickness, and an implant componentsurface curvature that adjusts the mechanical axis or axes intoalignment in one or more planes. For example, a lower limb misalignmentcan be corrected in a knee replacement by designing or selecting one ormore of a femoral resection dimension, a femoral implant componentthickness, a femoral implant component surface curvature, a tibialresection dimension, a tibial implant component thickness, a tibialimplant component insert thickness, and a tibial implant componentsurface curvature to adjust the femoral mechanical axis and tibialmechanical axis into alignment in the coronal plane.

FIG. 16 illustrates a coronal plane of the knee with exemplary resectioncuts that can be used to correct lower limb alignment in a kneereplacement. As shown in the figure, the selected and/or designedresection cuts can include different cuts on different portions of apatient's biological structure. For example, resection cut facets onmedial and lateral femoral condyles can be non-coplanar and parallel1602, 1602′, angled 1604, 1604′, or non-coplanar and non-parallel, forexample, cuts 1602 and 1604′ or cuts 1602′ and 1604. Similar, resectioncut facets on medial and lateral portions of the tibia can benon-coplanar and parallel 1606, 1606′, angled and parallel 1608, 1608′,or non-coplanar and non-parallel, for example, cuts 1606 and 1608′ orcuts 1606′ and 1608. Non-coplanar facets of resection cuts can include astep-cut 1610 to connect the non-coplanar resection facet surfaces.Selected and/or designed resection dimensions can be achieved using ormore selected and/or designed guide tools (e.g., cutting jigs) thatguide resectioning (e.g., guide cutting tools) of the patient'sbiological structure to yield the predetermined resection surfacedimensions (e.g., resection surface(s), angles, and/or orientation(s).In certain embodiments, the bone-facing surfaces of the implantcomponents can be designed to include one or more features (e.g., bonecut surface areas, perimeters, angles, and/or orientations) thatsubstantially match one or more of the resection cut or cut facets thatwere predetermined to enhance the patient's alignment. As shown in FIG.16, certain combinations of resection cuts can aid in bringing thefemoral mechanical axis 1612 and tibial mechanical axis 1614 intoalignment 1616.

Alternatively, or in addition, certain implant features, such asdifferent implant thicknesses and/or surface curvatures across twodifferent sides of the plane in which the mechanical axes 1612, 1614 aremisaligned also can aid correcting limb alignment. For example, FIG. 17depicts a coronal plane of the knee shown with femoral implant medialand lateral condyles 1702, 1702′ having different thicknesses to help tocorrect limb alignment. These features can be used in combination withany of the resection cut 1704, 1704′ described above and/or incombination with different thicknesses on the corresponding portions ofthe tibial component. As described more fully below, independent tibialimplant components and/or independent tibial inserts on medial andlateral sides of the tibial implant component can be used enhancealignment at a patient's knee joint. An implant component can includeconstant yet different thicknesses in two or more portions of theimplant (e.g., a constant medial condyle thickness different from aconstant lateral condyle thickness), a gradually increasing thicknessacross the implant or a portion of the implant, or a combination ofconstant and gradually increasing thicknesses.

FIG. 18 illustrates a virtual model of a patient's limb that ismisaligned in the sagittal plane, for example, a genu antecurvatumdeformity, and the virtually corrected limb. The deformity correctioncan be achieved using a similar design approach as described above for acoronal plane deformity. However, the selection and/or design of one ormore femoral resection dimensions, femoral implant componentthicknesses, femoral implant component surface curvatures, tibialresection dimensions, tibial implant component thicknesses, tibialimplant component insert thicknesses, and/or tibial implant componentsurface curvatures can be used to adjust the femoral mechanical axis andtibial mechanical axis into alignment in the sagittal plane (e.g., byaltering corresponding features across the sagittal plane, for example,by altering anterior features relative to corresponding posteriorfeatures). Alignment deformities in both the coronal and sagittalplanes, or in multiple planes about the mechanical axes, can beaddressed by designing and/or selecting one or more resectiondimensions, one or more implant component thicknesses, and/or one ormore implant component surface curvatures.

In certain embodiments, an implant component that is preoperativelydesigned and/or selected to correct a patient's alignment also can bedesigned or selected to include additional patient-specific orpatient-engineered features. For example, the bone-facing surface of animplant or implant component can be designed and/or selected tosubstantially negatively-match the resected bone surface. As depicted inFIG. 19A, the perimeters and areas 1910 of two bone surface areas isdifferent for two different bone resection cut depths 1920. Similarly,FIG. 19B depicts a distal view of the femur in which two differentresection cuts are applied. As shown, the resected perimeters andsurface areas for two distal facet resection depths are different foreach of the medial condyle distal cut facet 1930 and the lateral condyledistal cut facet 1940.

If resection dimensions are angled, for example, in the coronal planeand/or in the sagittal plane, various features of the implant component,for example, the component bone-facing surface, can be designed and/orselected based on an angled orientation into the joint rather than on aperpendicular orientation For example, the perimeter of tibial implantor implant component that substantially positively-matches the perimeterof the patient's cut tibial bone has a different shape depending on theangle of the cut. Similarly, with a femoral implant component, the depthor angle of the distal condyle resection on the medial and/or lateralcondyle can be designed and/or selected to correct a patient alignmentdeformity. However, in so doing, one or more of the implant or implantcomponent condyle width, length, curvature, and angle of impact againstthe tibia can be altered. Accordingly in certain embodiments, one ormore implant or implant component features, such as implant perimeter,condyle length, condyle width, curvature, and angle is designed and/orselected relative to the a sloping and/or non-coplanar resection cut.

4.2 Preserving Bone, Cartilage or Ligament

Traditional orthopedic implants incorporate bone cuts. These bone cutsachieve two objectives: they establish a shape of the bone that isadapted to the implant and they help achieve a normal or near normalaxis alignment. For example, bone cuts can be used with a knee implantto correct an underlying varus of valgus deformity and to shape thearticular surface of the bone to fit a standard, bone-facing surface ofa traditional implant component. With a traditional implant, multiplebone cuts are placed. However, since traditional implants aremanufactured off-the-shelf without use of patient-specific information,these bone cuts are pre-set for a given implant without taking intoconsideration the unique shape of the patient. Thus, by cutting thepatient's bone to fit the traditional implant, more bone is discardedthan is necessary with an implant designed to address the particularlypatient's structures and deficiencies.

In certain embodiments, resection cuts are optimized to preserve themaximum amount of bone for each individual patient, based on a series oftwo-dimensional images or a three-dimensional representation of thepatient's articular anatomy and geometry and the desired limb alignmentand/or desired deformity correction. Resection cuts on two opposingarticular surfaces can be optimized to achieve the minimum amount ofbone resected from one or both articular surfaces.

By adapting resection cuts in the series of two-dimensional images orthe three-dimensional representation on two opposing articular surfacessuch as, for example, a femoral head and an acetabulum, one or bothfemoral condyle(s) and a tibial plateau, a trochlea and a patella, aglenoid and a humeral head, a talar dome and a tibial plafond, a distalhumerus and a radial head and/or an ulna, or a radius and a scaphoid,certain embodiments allow for patient individualized, bone-preservingimplant designs that can assist with proper ligament balancing and thatcan help avoid “overstuffing” of the joint, while achieving optimal bonepreservation on one or more articular surfaces in each patient.

The resection cuts also can be designed to meet or exceed a certainminimum material thickness, for example, the minimum amount of thicknessrequired to ensure biomechanical stability and durability of theimplant. In certain embodiments, the limiting minimum implant thicknesscan be defined at the intersection of two adjoining bone cuts on theinner, bone-facing surface of an implant component. For example, in thefemoral implant component 2000 shown in FIG. 20, the minimum thicknessof the implant component appears at one or more intersections 2100. Incertain embodiments of a femoral implant component, the minimum implantthickness can be less than 10 mm, less than 9 mm, less than 8 mm, lessthan 7 mm, and/or less than 6 mm.

These optimizations can be performed for one, two, or three opposingarticular surfaces, for example, in a knee they can be performed on atibia, a femur and a patella.

In a knee, different resection cuts can be planned for a medial andlateral femoral condyle. In certain embodiments, a single bone cut canbe optimized in a patient to maximize bone preservation in that selectarea, for example, a posterior condyle. Alternatively, multiple or allresection cuts can be optimized. Since a patient's medial and lateralfemoral condyles typically have different geometries, including, forexample, width, length and radii of curvature in multiple planes, forexample, the coronal and the sagittal plane, then one or more resectioncuts can be optimized in the femur individually for each condyle,resulting in resection cuts placed at a different depths, angles, and/ororientations in one condyle relative to the other condyle. For example,a horizontal cut in a medial condyle may be anatomically placed moreinferior relative to the limb than a horizontal cut in a lateralcondyle. The distance of the horizontal cut from the subchondral bonemay be the same in each condyle or it can be different in each condyle.Chamfer cuts in the medial and lateral condyle may be placed indifferent planes rather than the same plane in order to optimize bonepreservation. Moreover, chamfer cuts in the medial and lateral condylemay be placed at a different angle in order to maximize bonepreservation. Posterior cuts may be placed in a different plane,parallel or non-parallel, in a medial and a lateral femoral condyle inorder to maximize bone preservation. A medial condyle may include morebone cut facets than a lateral condyle in order to enhance bonepreservation or vice versa.

In certain embodiments, a measure of bone preservation can include totalvolume of bone resected, volume of bone resected from one or moreresection cuts, volume of bone resected to fit one or more implantcomponent bone cuts, average thickness of bone resected, averagethickness of bone resected from one or more resection cuts, averagethickness of bone resected to fit one or more implant component bonecuts, maximum thickness of bone resected, maximum thickness of boneresected from one or more resection cuts, maximum thickness of boneresected to fit one or more implant component bone cuts.

Certain embodiments of femoral implant components described hereininclude more than five bone cuts, for example, six, seven, eight, nineor more bone cuts on the inner, bone-facing surface of the implantcomponent. These bone cuts can be standard, in whole or in part, orpatient-adapted, in whole or in part. Alternatively, certain embodimentsinclude five bone cuts that are patient-adapted based on one or moreimages of the patient's knee. A femoral implant component with greaterthan five bone cuts of and/or with patient-adapted bone cuts can allowfor enhanced bone preservation over a traditional femoral implant withfive standard bone cuts and therefore can perform as a pre-primaryimplant.

A patient-specific implant having bone cuts that are non-parallel to thecuts of a subsequent primary can result in the primary implant havingsmall gaps between the bone and the inner, bone-facing surface of theprimary implant. These small gaps can result misalignment intersectsbetween the pre-primary implant and the subsequent primary implant. Forexample, as shown in FIG. 21, the bone cuts (shown in red) for apre-primary implant component having a 5-flex cut can retain bone ascompared to a traditional primary implant (shown in outline), but asmall gap 2110 also can be created by the pre-primary cut. Any suchsmall gaps 2120 can be filled with bone cement when fitting a subsequentprimary implant.

In addition to optimizing bone preservation, another factor indetermining the depth, number, and/or orientation of resection cutsand/or implant component bone cuts is desired implant thickness. Aminimum implant thickness can be included as part of the resection cutand/or bone cut design to ensure a threshold strength for the implant inthe face of the stresses and forces associated with joint motion, suchas standing, walking, and running. Table 5 shows the results of a finiteelement analysis (FEA) assessment for femoral implant components ofvarious sizes and with various bone cut numbers and orientations. Themaximum principal stress observed in FEA analysis can be used toestablish an acceptable minimum implant thickness for an implantcomponent having a particular size and, optionally, for a particularpatient (e.g., having a particular weight, age, activity level, etc).Before, during, and/or after establishing a minimum implant componentthickness, the optimum depth of the resection cuts and the optimumnumber and orientation of the resection cuts and bone cuts, for example,for maximum bone preservation, can designed.

In certain embodiments, an implant component design or selection candepend, at least in part, on a threshold minimum implant componentthickness. In turn, the threshold minimum implant component thicknesscan depend, at least in part, on patient-specific data, such as condylarwidth, femoral transepicondylar axis length, and/or the patient'sspecific weight. In this way, the threshold implant thickness, and/orany implant component feature, can be adapted to a particular patientbased on a combination of patient-specific geometric data and onpatient-specific anthropometric data. This approach can apply to anyimplant component feature for any joint, for example, the knee, the hip,or the shoulder.

TABLE 5 Finite Element Analysis for Various Implant Designs MaximumDistal Principal Condyle Relative Scan Stress, Implant DescriptionGeomery Size # mPa 6-Cut, non-flexed coplanar Sigma #1.5 3017 161 5-Cut,non-flexed coplanar Sigma #1.5 3017 201 6-Cut, flexed 5 degrees coplanarSigma #1.5 3017 229 6-Cut, non-flexed coplanar Sigma #3 2825 221 5-Cut,non-flexed coplanar Sigma #3 2825 211 6-Cut, flexed 5 degrees coplanarSigma #3 2825 198 5-Cut, non flexed coplanar Sigma #7 1180 292 6-Cut,non-flexed coplanar Sigma #7 1180 221 6-Cut, flexed 5 degrees coplanarSigma #7 1180 214 7-Cut non-flexed coplanar Sigma #7 1180 203 6-Cut,non-flexed non- Sigma #7 1180 173 coplanar, w/step 7-cut, flexed 5degrees non- Sigma #7 1180 202 coplanar, w/out step

A weighting optionally can be applied to each bone with regard to thedegree of bone preservation achieved. For example, if the maximum ofbone preservation is desired on a tibia or a sub-segment of a tibia,femoral bone cuts can be adapted and moved accordingly to ensure properimplant alignment and ligament balancing. Conversely, if maximum bonepreservation is desired on a femoral condyle, a tibial bone cut can beadjusted accordingly. If maximum bone preservation is desired on apatella, a resection cut on the opposing trochlea can be adjustedaccordingly to ensure maximal patellar bone preservation withoutinducing any extension deficits. If maximum bone preservation is desiredon a trochlea, a resection cut on the opposing patella can be adjustedaccordingly to ensure maximal patellar bone preservation withoutinducing any extension deficits. Any combination is possible anddifferent weightings can be applied. The weightings can be applied usingmathematical models or, for example, data derived from patient referencedatabases.

Implant design and modeling also can be used to achieve ligamentsparing, for example, with regard to the PCL and/or the ACL. An imagingtest can be utilized to identify, for example, the origin and/or theinsertion of the PCL and the ACL on the femur and tibia.

The origin and the insertion can be identified by visualizing, forexample, the ligaments directly, as is possible with MRI or spiral CTarthrography, or by visualizing bony landmarks known to be the origin orinsertion of the ligament such as the medial and lateral tibial spines.

An implant system can then be selected or designed based on the imagedata so that, for example, the femoral component preserves the ACLand/or PCL origin, and the tibial component preserves the ACL and/or PCLattachment. The implant can be selected or designed so that bone cutsadjacent to the ACL or PCL attachment or origin do not weaken the boneto induce a potential fracture.

For ACL preservation, the implant can have two unicompartmental tibialcomponents that can be selected or designed and placed using the imagedata. Alternatively, the implant can have an anterior bridge component.The width of the anterior bridge in AP dimension, its thickness in thesuperoinferior dimension or its length in mediolateral dimension can beselected or designed using the imaging data and, specifically, the knowninsertion of the ACL and/or PCL.

As can be seen in FIGS. 22A and 22B, the posterior margin of an implantcomponent, e.g. a polyethylene- or metal-backed tray with polyethyleneinserts, can be selected and/or designed using the imaging data orshapes derived from the imaging data so that the implant component willnot interfere with and stay clear of the PCL. This can be achieved, forexample, by including concavities in the outline of the implant that arespecifically designed or selected or adapted to avoid the ligamentinsertion.

Any implant component can be selected and/or adapted in shape so that itstays clear of important ligament structures. Imaging data can helpidentify or derive shape or location information on such ligamentousstructures. For example, the lateral femoral condyle of aunicompartmental, bicompartmental or total knee system can include aconcavity or divet to avoid the popliteus tendon. In a shoulder, theglenoid component can include a shape or concavity or divet to avoid asubscapularis tendon or a biceps tendon. In a hip, the femoral componentcan be selected or designed to avoid an iliopsoas or adductor tendons.

4.3 Establishing Normal or Near-Normal Joint Kinematics

In certain embodiments, bone cuts and implant shape including at leastone of a bone-facing or a joint-facing surface of the implant can bedesigned or selected to achieve normal joint kinematics.

In certain embodiments, a computer program simulating biomotion of oneor more joints, such as, for example, a knee joint, or a knee and anklejoint, or a hip, knee and/or ankle joint can be utilized. In certainembodiments, patient-specific imaging data can be fed into this computerprogram. For example, a series of two-dimensional images of a patient'sknee joint or a three-dimensional representation of a patient's kneejoint can be entered into the program. Additionally, two-dimensionalimages or a three-dimensional representation of the patient's anklejoint and/or hip joint may be added.

Alternatively, patient-specific kinematic data, for example obtained ina gait lab, can be fed into the computer program. Alternatively,patient-specific navigation data, for example generated using a surgicalnavigation system, image guided or non-image guided can be fed into thecomputer program. This kinematic or navigation data can, for example, begenerated by applying optical or RF markers to the limb and byregistering the markers and then measuring limb movements, for example,flexion, extension, abduction, adduction, rotation, and other limbmovements.

Optionally, other data including anthropometric data may be added foreach patient. These data can include but are not limited to thepatient's age, gender, weight, height, size, body mass index, and race.Desired limb alignment and/or deformity correction can be added into themodel. The position of bone cuts on one or more articular surfaces aswell as the intended location of implant bearing surfaces on one or morearticular surfaces can be entered into the model.

A patient-specific biomotion model can be derived that includescombinations of parameters listed above. The biomotion model cansimulate various activities of daily life including normal gait, stairclimbing, descending stairs, running, kneeling, squatting, sitting andany other physical activity. The biomotion model can start out withstandardized activities, typically derived from reference databases.These reference databases can be, for example, generated using biomotionmeasurements using force plates and motion trackers using radiofrequencyor optical markers and video equipment.

The biomotion model can then be individualized with use ofpatient-specific information including at least one of, but not limitedto the patient's age, gender, weight, height, body mass index, and race,the desired limb alignment or deformity correction, and the patient'simaging data, for example, a series of two-dimensional images or athree-dimensional representation of the joint for which surgery iscontemplated.

An implant shape including associated bone cuts generated in thepreceding optimizations, for example, limb alignment, deformitycorrection, bone preservation on one or more articular surfaces, can beintroduced into the model. Table 6 includes an exemplary list ofparameters that can be measured in a patient-specific biomotion model.

TABLE 6 Parameters measured in a patient-specific biomotion model forvarious implants Joint implant Measured Parameter knee Medial femoralrollback during flexion knee Lateral femoral rollback during flexionknee Patellar position, medial, lateral, superior, inferior fordifferent flexion and extension angles knee Internal and externalrotation of one or more femoral condyles knee Internal and externalrotation of the tibia knee Flexion and extension angles of one or morearticular surfaces knee Anterior slide and posterior slide of at leastone of the medial and lateral femoral condyles during flexion orextension knee Medial and lateral laxity throughout the range of motionknee Contact pressure or forces on at least one or more articularsurfaces, e.g. a femoral condyle and a tibial plateau, a trochlea and apatella knee Contact area on at least one or more articular surfaces,e.g. a femoral condyle and a tibial plateau, a trochlea and a patellaknee Forces between the bone-facing surface of the implant, an optionalcement interface and the adjacent bone or bone marrow, measured at leastone or multiple bone cut or bone-facing surface of the implant on atleast one or multiple articular surfaces or implant components. kneeLigament location, e.g. ACL, PCL, MCL, LCL, retinacula, joint capsule,estimated or derived, for example using an imaging test. knee Ligamenttension, strain, shear force, estimated failure forces, loads forexample for different angles of flexion, extension, rotation, abduction,adduction, with the different positions or movements optionallysimulated in a virtual environment. knee Potential implant impingementon other articular structures, e.g. in high flexion, high extension,internal or external rotation, abduction or adduction or anycombinations thereof or other angles/positions/movements. Hip, shoulderor Internal and external rotation of one or more articular surfacesother joint Hip, shoulder or Flexion and extension angles of one or morearticular surfaces other joint Hip, shoulder or Anterior slide andposterior slide of at least one or more articular surfaces other jointduring flexion or extension, abduction or adduction, elevation, internalor external rotation Hip, shoulder or Joint laxity throughout the rangeof motion other joint Hip, shoulder or Contact pressure or forces on atleast one or more articular surfaces, e.g. an other joint acetabulum anda femoral head, a glenoid and a humeral head Hip, shoulder or Forcesbetween the bone-facing surface of the implant, an optional cement otherjoint interface and the adjacent bone or bone marrow, measured at leastone or multiple bone cut or bone-facing surface of the implant on atleast one or multiple articular surfaces or implant components. Hip,shoulder or Ligament location, e.g. transverse ligament, glenohumeralligaments, other joint retinacula, joint capsule, estimated or derived,for example using an imaging test. Hip, shoulder or Ligament tension,strain, shear force, estimated failure forces, loads for other jointexample for different angles of flexion, extension, rotation, abduction,adduction, with the different positions or movements optionallysimulated in a virtual environment. Hip, shoulder or Potential implantimpingement on other articular structures, e.g. in high other jointflexion, high extension, internal or external rotation, abduction oradduction or elevation or any combinations thereof or otherangles/positions/ movements.

The above list is not meant to be exhaustive, but only exemplary. Anyother biomechanical parameter known in the art can be included in theanalysis.

The resultant biomotion data can be used to further optimize the implantdesign with the objective to establish normal or near normal kinematics.The implant optimizations can include one or multiple implantcomponents. Implant optimizations based on patient-specific dataincluding image based biomotion data include, but are not limited to:

-   -   Changes to external, joint-facing implant shape in coronal plane    -   Changes to external, joint-facing implant shape in sagittal        plane    -   Changes to external, joint-facing implant shape in axial plane    -   Changes to external, joint-facing implant shape in multiple        planes or three dimensions    -   Changes to internal, bone-facing implant shape in coronal plane    -   Changes to internal, bone-facing implant shape in sagittal plane    -   Changes to internal, bone-facing implant shape in axial plane    -   Changes to internal, bone-facing implant shape in multiple        planes or three dimensions    -   Changes to one or more bone cuts, for example with regard to        depth of cut, orientation of cut

Any single one or combinations of the above or all of the above on atleast one articular surface or implant component or multiple articularsurfaces or implant components.

When changes are made on multiple articular surfaces or implantcomponents, these can be made in reference to or linked to each other.For example, in the knee, a change made to a femoral bone cut based onpatient-specific biomotion data can be referenced to or linked with aconcomitant change to a bone cut on an opposing tibial surface, forexample, if less femoral bone is resected, the computer program mayelect to resect more tibial bone.

Similarly, if a femoral implant shape is changed, for example on anexternal surface, this can be accompanied by a change in the tibialcomponent shape. This is, for example, particularly applicable when atleast portions of the tibial bearing surface negatively-match thefemoral joint-facing surface.

Similarly, if the footprint of a femoral implant is broadened, this canbe accompanied by a widening of the bearing surface of a tibialcomponent. Similarly, if a tibial implant shape is changed, for exampleon an external surface, this can be accompanied by a change in thefemoral component shape. This is, for example, particularly applicablewhen at least portions of the femoral bearing surface negatively-matchthe tibial joint-facing surface.

Similarly, if a patellar component radius is widened, this can beaccompanied by a widening of an opposing trochlear bearing surfaceradius, or vice-versa.

These linked changes also can apply for hip and/or shoulder implants.For example, in a hip, if a femoral implant shape is changed, forexample on an external surface, this can be accompanied by a change inan acetabular component shape. This is, for example, particularlyapplicable when at least portions of the acetabular bearing surfacenegatively-match the femoral joint-facing surface. In a shoulder, if aglenoid implant shape is changed, for example on an external surface,this can be accompanied by a change in a humeral component shape. Thisis, for example, particularly applicable when at least portions of thehumeral bearing surface negatively-match the glenoid joint-facingsurface, or vice-versa.

Any combination is possible as it pertains to the shape, orientation,and size of implant components on two or more opposing surfaces.

By optimizing implant shape in this manner, it is possible to establishnormal or near normal kinematics. Moreover, it is possible to avoidimplant related complications, including but not limited to anteriornotching, notch impingement, posterior femoral component impingement inhigh flexion, and other complications associated with existing implantdesigns. For example, certain designs of the femoral components oftraditional knee implants have attempted to address limitationsassociated with traditional knee implants in high flexion by alteringthe thickness of the distal and/or posterior condyles of the femoralimplant component or by altering the height of the posterior condyles ofthe femoral implant component. Since such traditional implants follow aone-size-fits-all approach, they are limited to altering only one or twoaspects of an implant design. However, with the design approachesdescribed herein, various features of an implant component can bedesigned for an individual to address multiple issues, including issuesassociated with high flexion motion. For example, designs as describedherein can alter an implant component's bone-facing surface (forexample, number, angle, and orientation of bone cuts), joint-facingsurface (for example, surface contour and curvatures) and other features(for example, implant height, width, and other features) to addressissues with high flexion together with other issues.

Biomotion models for a particular patient can be supplemented withpatient-specific finite element modeling or other biomechanical modelsknown in the art. Resultant forces in the knee joint can be calculatedfor each component for each specific patient. The implant can beengineered to the patient's load and force demands. For instance, a 125lb. patient may not need a tibial plateau as thick as a patient with 280lbs. Similarly, the polyethylene can be adjusted in shape, thickness andmaterial properties for each patient. For example, a 3 mm polyethyleneinsert can be used in a light patient with low force and a heavier ormore active patient may need an 8 mm polymer insert or similar device.

4.4 Restoration or Optimization of Joint-Line Location and Joint GapWidth

Traditional implants frequently can alter the location of a patient'sexisting or natural joint-line. For example, with a traditional implanta patient's joint-line can be offset proximally or distally as comparedto the corresponding joint-line on the corresponding limb. This cancause mechanical asymmetry between the limbs and result in unevenmovement or mechanical instability when the limbs are used together. Anoffset joint-line with a traditional implant also can cause thepatient's body to appear symmetrical.

Traditional implants frequently alter the location of a patient'sexisting or natural joint-line because they have a standard thicknessthat is thicker or thinner than the bone and/or cartilage that they arereplacing. For example, a schematic of a traditional implant componentis shown in FIGS. 23A and 23B. In the figure, the dashed line representsthe patient's existing or natural joint-line 2340 and the dotted linerepresents the offset joint-line 2342 following insertion of thetraditional implant component 2350. As shown in FIG. 23A, thetraditional implant component 2350 with a standard thickness replaces aresected piece 2352 of a first biological structure 2354 at anarticulation between the first biological structure 2354 and a secondbiological structure 2356. The resected piece 2352 of the biologicalstructure can include, for example, bone and/or cartilage, and thebiological structure 2354 can include bone and/or cartilage. In thefigure, the standard thickness of the traditional implant component 2350differs from the thickness of the resected piece 2352.

Therefore, as shown in FIG. 23B, the replacement of the resected piece2352 with the traditional implant component 2350 creates a wider jointgap 2358 and/or an offset joint-line. Surgeons can address the widenedjoint gap 2358 by pulling the second biological structure 2356 towardthe first biological structure 2354 and tightening the ligamentsassociated with the joint. However, while this alteration restores someof the mechanical instability created by a widened joint gap, it alsoexacerbates the displacement of the joint-line.

Certain embodiments are directed to implant components, and relateddesigns and methods, having one or more features that are engineeredfrom patient-specific data to restore or optimize the particularpatient's joint-line location. In addition or alternatively, certainpatient-specific implant components, and related designs and methods,can have one or more features that are engineered from patient-specificdata to restore or optimize the particular patient's joint gap width.

In certain embodiments, an implant component can be designed based onpatient-specific data to include a thickness profile between itsjoint-facing surface and its bone-facing surface to restore and/oroptimize the particular patient's joint-line location. For example, asschematically depicted in FIG. 23C, the thickness profile (shown as A)of the patient-specific implant component 2360 can be designed to, atleast in part, substantially positively-match the distance from thepatient's existing or natural joint-line 2340 to the articular surfaceof the biological structure 2354 that the implant 2360 engages. In theschematic depicted in the figure, the patient joint gap width also isretained.

The matching thickness profile can be designed based on one or more ofthe following considerations: the thickness (shown as A′ in FIG. 23C) ofa resected piece of biological structure that the implant replaces; thethickness of absent or decayed biological structure that the implantreplaces; the relative compressibility of the implant material(s) andthe biological material(s) that the implant replaces; and the thicknessof the saw blade(s) used for resectioning and/or material lost inremoving a resected piece.

For embodiments directed to an implant component thickness that isengineered based on patient-specific data to optimize joint-linelocation (and/or other parameters such as preserving bone), the minimumacceptable thickness of the implant can be a significant consideration.Minimal acceptable thickness can be determined based on any criteria,such as a minimum mechanical strength, for example, as determined byFEA. Accordingly, in certain embodiments, an implant or implant designincludes an implant component having a minimal thickness profile. Forexample, in certain embodiments a pre-primary or primary femoral implantcomponent can include a thickness between the joint-facing surface andthe bone-facing surface of the implant component that is less than 5 mm,less than 4 mm, less than 3 mm, and/or less than 2 mm.

In certain embodiments, the implant component thickness can range fromabout 2 mm to about 3 mm. Therefore, for patients that require onlyminimal bone resectioning of no more than 2-3 mm depth from thejoint-line, an implant component designed with a thickness tosubstantially positively-match the 2-3 mm bone resectioning can maintainthe joint-line location. Moreover, a subsequent traditional primaryimplant, for example, of 5 mm or greater thickness can be applied laterwith an additional cut depth of 3-2 mm or greater (for a total 5 mm cutdepth). This can allow for maintenance of the joint-line with thesubsequent, traditional primary as well.

Certain embodiments directed to implants or implant designs optimized toachieve minimal implant thickness can include a higher number of bonecuts, for example, six, seven, eight, nine or more bone cuts, on theinner, bone-facing surface of the implant. The bone cuts can be orientedin various dimensions, for example, in a flexed-orientation. Moreover,certain embodiments can include on the inner, bone-facing surface anycombination of straight cuts and curvilinear cuts. One or morecurvilinear cuts can be designed to substantially positively-match thepatient's uncut articular surface, such as a subchondral bone surfaceexposed by resurfacing. Alternatively, one or more curvilinear cuts canbe designed to substantially positively-match a cut surface of thepatient's bone, for example, a cut curvilinear surface. Example 5describes an example of an implant and implant design that includes astraight anterior cut, a straight posterior cut, and a curvilinear cutin between. Moreover, as depicted in FIG. 24, an implant 2400 caninclude a planar distal cut 2410, a straight anterior cut 2420, astraight posterior cut 2430, and curvilinear chamfer cuts 2440 inbetween to substantially negatively-match corresponding resectedsurface(s) of the femur 2450. Example 6 describes an example of animplant or implant design that includes on the inner, bone-facingsurface one or no straight cuts and portions that substantiallypositively-match an uncut articular bone surface.

The inner, bone-facing surface of the implant component can be designedto substantially negatively-match the cut bone surface, both curved andstraight portions. The curved cuts to the bone can be performed with arouter saw, as described in Example 5. Any number of the cuts can have adepth of 2-3 mm, and the implant component thickness can be designed topositively-match the cut depth across a portion of the implant or acrossthe entire implant.

By positively-matching the implant component thickness profile with thecut depth profile, and by negatively-matching the component bone-facingsurface with the resected articular surface of the biological structure,certain features of the component joint-facing surface canpositively-match the corresponding biological features that it replaces.For example, if the component bone-facing surface and thickness matchthe corresponding features of the biological structure, the componentjoint-facing curvature, such as a j-curve, also can match thecorresponding surface curvature of the patient's biological structure.

In certain embodiments, one or more implant components can be designedbased on patient-specific data to include a thickness profile thatretains, restores, and/or optimizes the particular patient's joint gapwidth. For example, as schematically depicted in FIGS. 25A and 25B, thepatient-specific implant components 2585, 2586 can be designed to, atleast in part, substantially positively-match the patient's existing ornatural joint gap 2588. In the figure, the dashed line represents thepatient's existing or natural joint-line 2590. The patient-specificimplant components 2585, 2586 do not have thicknesses that match thecorresponding resected pieces 2592, 2594 of biological structures 2596,2598. However, as shown in FIG. 25B, the implant components 2585, 2586are designed to retain the patient's specific gap width 2588.

If the thickness of an implant component is greater than the depth ofthe corresponding bone cut, then the thicker implant component can shiftthe joint-line down. However, as shown in FIGS. 25A and 25B, the jointgap width can be retained by designing a second implant component tooffset the greater thickness of the first implant component. Forexample, in total knee replacements that include both a femoral implantcomponent and a tibial implant component, if the femoral implantcomponent is thicker than the depth of the corresponding bone cut, moretibial bone can be cut and/or a thinner tibial implant can be used.

One or more components of a tibial implant can be designed thinner toretain, restore, and/or optimize a patient's joint-line and/or joint gapwidth. For example, one or both of a tibial tray and a tibial trayinsert (e.g., a poly insert) can be designed and/or selected (e.g.,preoperatively selected) to be thinner in one or more locations in orderto address joint-line and/or joint-gap issues for a particular patient.In certain embodiments, a tibial bone cut and/or the thickness of acorresponding portion of a tibial implant component may be less thanabout 6 mm, less than about 5 mm, less than about 4 mm, less than about3 mm, and/or less than about 2 mm.

In certain embodiments, one or more implant components can designedbased on patient-specific data to include a thickness profile thatretains or alters a particular patient's joint gap width to retain orcorrect another patient-specific feature. For example, thepatient-specific data can include data regarding the length of thepatient's corresponding limbs (e.g., left and right limbs) and theimplant component(s) can be designed to, at least in part, alter thelength of one limb to better match the length of the corresponding limb.

5. Selecting and/or Designing an Implant Component and, Optionally,Related Surgical Steps and Guide Tools

Any combination of one or more of the above-identified parameters and/orone or more additional parameters can be used in the design and/orselection of a patient-adapted (e.g., patient-specific and/orpatient-engineered) implant component and, in certain embodiments, inthe design and/or selection of corresponding patient-adapted resectioncuts and/or patient-adapted guide tools. In particular assessments, apatient's biological features and feature measurements are used toselect and/or design one or more implant component features and featuremeasurements, resection cut features and feature measurements, and/orguide tool features and feature measurements.

In certain embodiments, the assessment process includes selecting and/ordesigning one or more features and/or feature measurements of an implantcomponent and, optionally, of a corresponding resection cut strategyand/or guide tool that is adapted (e.g., patient-adapted based on one ormore of a particular patient's biological features and/or featuremeasurements) to achieve or address, at least in part, one or more ofthe following parameters for the particular patient: (1) correction of ajoint deformity; (2) correction of a limb alignment deformity; (3)preservation of bone, cartilage, and/or ligaments at the joint; (4)preservation, restoration, or enhancement of one or more features of thepatient's biology, for example, trochlea and trochlear shape; (5)preservation, restoration, or enhancement of joint kinematics,including, for example, ligament function and implant impingement; (6)preservation, restoration, or enhancement of the patient's joint-linelocation and/or joint gap width; and (7) preservation, restoration, orenhancement of other target features.

Correcting a joint deformity and/or a limb alignment deformity caninclude, for example, generating a virtual model of the patient's joint,limb, and/or other relevant biological structure(s); virtuallycorrecting the deformity and/or aligning the limb; and selecting and/ordesigning one or more surgical steps (e.g., one or more resection cuts),one or more guide tools, and/or one or more implant components tophysically perform and/or accommodate the correction.

Preserving, restoring, or enhancing bone, cartilage, and/or ligamentscan include, for example, identifying diseased tissue from one or moreimages of the patient's joint, identifying a minimum implant thicknessfor the patient (based on, for example, femur and/or condyle size andpatient weight); virtually assessing combinations of resection cuts andimplant component features, such as variable implant thickness, bone cutnumbers, bone cut angles, and/or bone cut orientations; identifying acombination of resection cuts and/or implant component features that,for example, remove diseased tissue and also provide maximum bonepreservation (i.e., minimum amount of resected bone) and at least theminimum implant thickness for the particular patient; and selectingand/or designing one or more surgical steps (e.g., one or more resectioncuts), one or more guide tools, and/or one or more implant components toprovide the resection cuts and/or implant component features thatprovide removal of the diseased tissue, maximum bone preservation, andat least the minimum implant thickness for the particular patient.

Preserving or restoring one or more features of a patient's biology caninclude, for example, selecting and/or designing one or more surgicalsteps (e.g., one or more resection cuts), one or more guide tools,and/or one or more implant components so that one or more of thepatient's postoperative implant features substantially match thepatient's preoperative biological features or the patient's healthybiological features (e.g., as identified from a previous image of thepatient's joint when it was healthy or from an image the patient'scontralateral healthy joint).

Enhancing one or more features of a patient's biology can include, forexample, selecting and/or designing one or more surgical steps (e.g.,one or more resection cuts), one or more guide tools, and/or one or moreimplant components so that the implant component, once implanted,includes features that approximate one or more features of a healthybiological feature for the particular patient.

Preservation or restoration of the patient's joint kinematics caninclude, for example, selecting and/or designing one or more surgicalsteps (e.g., one or more resection cuts), one or more guide tools,and/or one or more implant components so that the patient'spost-operative joint kinematics substantially match the patient'spre-operative joint kinematics and/or substantially match the patient'shealthy joint kinematics (e.g., as identified from previous images ofthe patient's joint when it was healthy or from an image the patient'scontralateral healthy joint).

Enhancing the patient's joint kinematics can include, for example,selecting and/or designing one or more surgical steps (e.g., one or moreresection cuts), one or more guide tools, and/or one or more implantcomponents that provide healthy joint kinematics estimated for theparticular patient and/or that provide proper joint kinematics to thepatient. Optimization of joint kinematics also can include optimizingligament loading or ligament function during motion.

Preservation or restoration of the patient's joint-line location and/orjoint gap width can include, for example, selecting and/or designing oneor more surgical steps (e.g., one or more resection cuts), one or moreguide tools, and/or one or more implant components so that the patient'sjoint-line and or joint-gap width substantially match the patient'sexisting joint-line and or joint-gap width or the patient's healthyjoint-line and/or joint-gap width (e.g., as identified from previousimages of the patient's joint when it was healthy or from an image thepatient's contralateral healthy joint).

Enhancing the patient's joint-line location and/or joint gap width caninclude, for example, selecting and/or designing one or more surgicalsteps (e.g., one or more resection cuts), one or more guide tools,and/or one or more implant components that provide a healthy joint-linelocation and/or joint gap width and/or estimated for the particularpatient and/or that provide proper kinematics to the patient.

5.1 Using Parameters to Assess and Select and/or Design an ImplantComponent

Assessment of the above-identified parameters, optionally with one ormore additional parameters, can be conducted using various formats. Forexample, the assessment of one or more parameters can be performed inseries, in parallel, or in a combination of serial and parallel steps,optionally with a software-directed computer. For example, one or moreselected implant component features and feature measurements, optionallywith one or more selected resection cut features and featuremeasurements and one or more selected guide tool features and featuremeasurements can be altered and assessed in series, in parallel, or in acombination format, to assess the fit between selected parameterthresholds and the selected features and feature measurements. Any oneor more of the parameters and features and/or feature measurements canbe the first to be selected and/or designed. Alternatively, one or more,or all, of the parameters and/or features can be assessedsimultaneously.

The assessment process can be iterative in nature. For example, one ormore first parameters can be assessed and the related implant componentand/or resection cut features and feature measurements tentatively orconditionally can be determined. Next, one or more second parameters canbe assessed and, optionally, one or more features and/or featuremeasurements determined. Then, the tentative or conditional featuresand/or feature measurements for the first assessed parameter(s)optionally can be altered based on the assessment and optionaldeterminations for the second assessed parameters. The assessmentprocess can be fully automated or it can be partially automated allowingfor user interaction. User interaction can be particularly useful forquality assurance purposes.

In the assessment, different weighting can be applied to any of theparameters or parameter thresholds, for example, based on the patient'sage, the surgeon's preference or the patient's preference. Feedbackmechanisms can be used to show the user or the software the effect thatcertain feature and/or feature measurement changes can have on desiredchanges to parameters values, e.g., relative to selected parameterthresholds. For example, a feedback mechanism can be used to determinethe effect that changes in features intended to maximize bonepreservation (e.g., implant component thickness(es), bone cut number,cut angles, cut orientations, and related resection cut number, angles,and orientations) have on other parameters such as limb alignment,deformity correction, and/or joint kinematic parameters, for example,relative to selected parameter thresholds. Accordingly, implantcomponent features and/or feature measurements (and, optionally,resection cut and guide tool features and/or feature measurements) canbe modeled virtually and modified reiteratively to achieve an optimumsolution for a particular patient.

FIG. 26 is a flow chart illustrating the process of assessing andselecting and/or designing one or more implant component features and/orfeature measurements, and, optionally assessing and selecting and/ordesigning one or more resection cut features and feature measurements,for a particular patient. Using the techniques described herein or thosesuitable and known in the art, one or more of the patient's biologicalfeatures and/or feature measurements are obtained 2600. In addition, oneor more variable implant component features and/or feature measurementsare obtained 2610. Optionally, one or more variable resection cutfeatures and/or feature measurements are obtained 2620. Moreover, one ormore variable guide tool features and/or feature measurements also canoptionally be obtained. Each one of these step can be repeated multipletimes, as desired.

The obtained patient's biological features and feature measurements,implant component features and feature measurements, and, optionally,resection cut and/or guide tool features and/or feature measurementsthen can be assessed to determine the optimum implant component featuresand/or feature measurements, and optionally, resection cut and/or guidetool features and/or feature measurements, that achieve one or moretarget or threshold values for parameters of interest 2630 (e.g., bymaintaining or restoring a patient's healthy joint feature). As noted,parameters of interest can include, for example, one or more of (1)joint deformity correction; (2) limb alignment correction; (3) bone,cartilage, and/or ligaments preservation at the joint; (4) preservation,restoration, or enhancement of one or more features of the patient'sbiology, for example, trochlea and trochlear shape; (5) preservation,restoration, or enhancement of joint kinematics, including, for example,ligament function and implant impingement; (6) preservation,restoration, or enhancement of the patient's joint-line location and/orjoint gap width; and (7) preservation, restoration, or enhancement ofother target features. This step can be repeated as desired. Forexample, the assessment step 2630 can be reiteratively repeated afterobtaining various feature and feature measurement information 2600,2610, 2620.

Once the one or more optimum implant component features and/or featuremeasurements are determined, the implant component(s) can be selected2640, designed 2650, or selected and designed 2640, 2650. For example,an implant component having some optimum features and/or featuremeasurements can be designed using one or more CAD software programs orother specialized software to optimize additional features or featuremeasurements of the implant component. One or more manufacturingtechniques described herein or known in the art can be used in thedesign step to produce the additional optimized features and/or featuremeasurements. This process can be repeated as desired.

Optionally, one or more resection cut features and/or featuremeasurements can be selected 2660, designed 2670, or selected andfurther designed 2660, 2670. For example, a resection cut strategyselected to have some optimum features and/or feature measurements canbe designed further using one or more CAD software programs or otherspecialized software to optimize additional features or measurements ofthe resection cuts, for example, so that the resected surfacessubstantially match optimized bone-facing surfaces of the selected anddesigned implant component. This process can be repeated as desired.

Moreover, optionally, one or more guide tool features and/or featuremeasurements can be selected, designed, or selected and furtherdesigned. For example, a guide tool having some optimum features and/orfeature measurements can be designed further using one or more CADsoftware programs or other specialized software to optimize additionalfeatures or feature measurements of the guide tool. One or moremanufacturing techniques described herein or known in the art can beused in the design step to produce the additional, optimized featuresand/or feature measurements, for example, to facilitate one or moreresection cuts that, optionally, substantially match one or moreoptimized bone-facing surfaces of a selected and designed implantcomponent. This process can be repeated as desired.

As will be appreciated by those of skill in the art, the process ofselecting and/or designing an implant component feature and/or featuremeasurement, resection cut feature and/or feature measurement, and/orguide tool feature and/or feature measurement can be tested against theinformation obtained regarding the patient's biological features, forexample, from one or more MRI or CT or x-ray images from the patient, toensure that the features and/or feature measurements are optimum withrespect to the selected parameter targets or thresholds. Testing can beaccomplished by, for example, superimposing the implant image over theimage for the patient's joint. Once optimum features and/or featuremeasurements for the implant component, and optionally for the resectioncuts and/or guide tools, have been selected and/or designed, the implantsite can be prepared, for example by removing cartilage and/orresectioning bone from the joint surface, and the implant component canbe implanted into the joint 2680.

The joint implant component bone-facing surface, and optionally theresection cuts and guide tools, can be selected and/or designed toinclude one or more features that achieve an anatomic or near anatomicfit with the existing surface or with a resected surface of the joint.Moreover, the joint implant component joint-facing surface, andoptionally the resection cuts and guide tools, can be selected and/ordesigned, for example, to replicate the patient's existing jointanatomy, to replicate the patient's healthy joint anatomy, to enhancethe patient's joint anatomy, and/or to optimize fit with an opposingimplant component. Accordingly, both the existing surface of the jointand the desired resulting surface of the joint can be assessed. Thistechnique can be particularly useful for implants that are not anchoredinto the bone.

As will be appreciated by those of skill in the art, the physician, orother person can obtain a measurement of a biological feature (e.g., atarget joint) 2600 and then directly select 2640, design, 2650, orselect and design 2640, 2650 a joint implant component having desiredpatient-adapted features and/or feature measurements. Designing caninclude, for example, design and manufacturing.

5.2 Setting and Weighing Parameters

As described herein, certain embodiments can apply modeling, forexample, virtual modeling and/or mathematical modeling, to identifyoptimum implant component features and measurements, and optionallyresection features and measurements, to achieve or advance one or moreparameter targets or thresholds. For example, a model of patient's jointor limb can be used to identify, select, and/or design one or moreoptimum features and/or feature measurements relative to selectedparameters for an implant component and, optionally, for correspondingresection cuts and/or guide tools. In certain embodiments, a physician,clinician, or other user can select one or more parameters, parameterthresholds or targets, and/or relative weightings for the parametersincluded in the model. Alternatively or in addition, clinical data, forexample obtained from clinical trials, or intraoperative data, can beincluded in selecting parameter targets or thresholds, and/or indetermining optimum features and/or feature measurements for an implantcomponent, resection cut, and/or guide tool.

Certain embodiments described herein include generating and/or using amodel, for example, a virtual model, of the patient's joint thatincludes selected parameters and/or parameter measurements and virtuallyselecting and/or designing one or more implant components, andoptionally resection cuts and/or guide tools to fit the virtual model inaccordance with the selected parameters and/or parameter measurements.This approach allows for iterative selection and/or design improvementand can include steps to virtually assess fit relative to the selectedparameters and/or parameter measurements, such as (1) correction of ajoint deformity; (2) correction of a limb alignment deformity; (3)preservation of bone, cartilage, and/or ligaments at the joint; (4)preservation, restoration, or enhancement of one or more features of thepatient's biology, for example, trochlea and trochlear shape; (5)preservation, restoration, or enhancement of joint kinematics,including, for example, ligament function and implant impingement; (6)preservation, restoration, or enhancement of the patient's joint-linelocation and/or joint gap width; and (7) preservation, restoration, orenhancement of other target features.

One or more parametric thresholds and/or weightings can be applied forthe selection and/or designing process. Different parameters can havethe same weighting or they can have different weightings. A parametercan include one or more thresholds for selecting one or more implants.The thresholds can include one or more minimum threshold values (e.g.,with different weightings), for example, 80%, greater than 80%, 85%,greater than 85%, 90%, greater than 90%, 95%, greater than 95%, 97%,greater than 97%, 98%, greater than 98%, 99%, greater than 99%, 100%,and/or greater than 100% a target value, such as minimum implantcoverage of a certain surface on the patient's anatomical structure.Alternatively or in addition, the thresholds can include one or moremaximum threshold values (e.g., with different weightings), such as105%, less than 105%, 103%, less than 103%, 102%, less than 102%, 101%,less than 101%, 100%, and/or less than 100% a target value, such asmaximum implant coverage of a certain surface on the patient'sanatomical structure.

One or more parameter thresholds can be absolute, for example, byselecting and/or designing for only implants that meet the threshold,for example, a threshold for a particular patient of 95% mediolateralfemoral condyle coverage all around the condyle(s). An example of aselection and/or design process having multiple absolute thresholds is aprocess that selects and/or designs femoral implant components that mustmeet both a minimum threshold for a particular patient of 95%mediolateral femoral condyle coverage in the central weight-bearingregion, and a minimum threshold of greater than 80% mediolateral femoralcondyle coverage outside the weight-bearing area.

Alternatively or in addition, one or more parameter thresholds can becontingent on one or more other factors. In particular, a selectionand/or designing process can successively search a library for implantsbased on contingent thresholds. For example, femoral implant componentsmeeting a minimum threshold of 99% mediolateral femoral condyle coverageinitially can be selected. If no implant meets the threshold, or if someimplants meet the threshold but do not meet other parameter thresholds,then a second selection round can include implants meeting a minimumthreshold of 98% mediolateral femoral condyle coverage. The process cancontinue to use additional, contingent thresholds until an implant withthe selected parameter thresholds is identified.

Different thresholds can be defined in different anatomic regions andfor different parameters. For example, in certain embodiments of a kneeimplant design, the amount of mediolateral tibial implant componentcoverage can be set at 90%, while the amount of anteroposterior tibialimplant component coverage can be set at 85%. In another illustrativeexample, the congruency in intercondylar notch shape can be set at 80%required, while the required mediolateral condylar coverage can be setat 95%.

5.3 Computer-Aided Optimization

Any of the methods described herein can be performed, at least in part,using a computer-readable medium having instructions stored thereon,which, when executed by one or more processors, causes the one or moreprocessors to perform one or more operations corresponding to one ormore steps in the method. Any of the methods can include the steps ofreceiving input from a device or user and producing an output for auser, for example, a physician, clinician, technician, or other user.Executed instructions on the computer-readable medium (i.e., a softwareprogram) can be used, for example, to receive as input patient-specificinformation (e.g., images of a patient's biological structure) andprovide as output a virtual model of the patient's biological structure.Similarly, executed instructions on a computer-readable medium can beused to receive as input patient-specific information and user-selectedand/or weighted parameters and then provide as output to a user valuesor ranges of values for those parameters and/or for resection cutfeatures, guide tool features, and/or implant component features. Forexample, in certain embodiments, patient-specific information can beinput into a computer software program for selecting and/or designingone or more resection cuts, guide tools, and/or implant components, andone or more of the following parameters can be optimization in thedesign process: (1) correction of joint deformity; (2) correction of alimb alignment deformity; (3) preservation of bone, cartilage, and/orligaments at the joint; (4) preservation, restoration, or enhancement ofone or more features of the patient's biology, for example, trochlea andtrochlear shape; (5) preservation, restoration, or enhancement of jointkinematics, including, for example, ligament function and implantimpingement; (6) preservation, restoration, or enhancement of thepatient's joint-line location and/or joint gap width; and (7)preservation, restoration, or enhancement of other target features.

Optimization of multiple parameters may result in conflictingconstraints; for example, optimizing one parameter may cause anundesired deviation to one or more other parameters. In cases where notall constraints can be achieved at the same time, parameters can beassigned a priority or weight in the software program. The priority orweighting can be automated (e.g., part of the computer program) and/orit can be selected by a user depending on the user's desired designgoals, for example, minimization of bone loss, or retention of existingjoint-line to preserve kinematics, or combination to accommodate bothparameters in overall design. As an illustrative example, in certainembodiments, selection and/or design of a knee implant can includeobtaining patient-specific information (e.g., from radiographic imagesor CT images) of a patient's knee and inputting that information intothe computer program to model features such as minimum thickness offemoral component (to minimize resected bone on femur), tibial resectioncut height (to minimize resected bone on tibia), and joint-line position(preferably to preserve for natural kinematics). These features can bemodeled and analyzed relative to a weighting of parameters such aspreserving bone and preserving joint kinematics. As output, one or moreresection cut features, guide tool features, and/or implant componentfeatures that optimize the identified parameters relative to theselective weightings can be provided.

In any automated process or process step performed by the computersystem, constraints pertaining to a specific implant model, to a groupof patients or to the individual patient may be taken into account. Forexample, the maximum implant thickness or allowable positions of implantanchors can depend on the type of implant. The minimum allowable implantthickness can depend on the patient's bone quality.

Any one or more steps of the assessment, selection, and/or design may bepartially or fully automated, for example, using a computer-run softwareprogram and/or one or more robots. For example, processing of thepatient data, the assessment of biological features and/or featuremeasurements, the assessment of implant component features and/orfeature measurements, the optional assessment of resection cut and/orguide tool features and/or feature measurements, the selection and/ordesign of one or more features of a patient -adapted implant component,and/or the implantation procedure(s) may be partially or whollyautomated. For example, patient data, with optional user-definedparameters, may be inputted or transferred by a user and/or byelectronic transfer into a software-directed computer system that canidentify variable implant component features and/or feature measurementsand perform operations to generate one or more virtual models and/orimplant design specifications, for example, in accordance with one ormore target or threshold parameters. Implant selection and/or designdata, with optional user-defined parameters, may be inputted ortransferred by a user and/or by electronic transfer into asoftware-directed computer system that performs a series of operationsto transform the data and optional parameters into one or more implantmanufacturing specifications. Implant design data or implantmanufacturing data, optionally with user-defined parameters, may beinputted or transferred by a user and/or by electronic transfer into asoftware-directed computer system that directs one or more manufacturinginstruments to produce one or more implant components from a startingmaterial, such as a raw material or starting blank material. Implantdesign data, implant manufacturing data, or implant data, optionallywith user-defined parameters, may be inputted or transferred by a userand/or by electronic transfer into a software-directed computer systemthat performs a series of operations to transform the data and optionalparameters into one or more surgical procedure specifications orinstructions. Implant design data, implant manufacturing data, implantdata, or surgical procedure data, optionally with user-definedparameters, may be inputted or transferred by a user and/or byelectronic transfer into a software-directed computer system thatdirects one or more automated surgical instruments, for example, arobot, to perform one or more surgical steps. In certain embodiments,one or more of these actions can be performed as steps in a singleprocess by one or more software -directed computer systems.

In certain embodiments, the implant component includes one or more bonecuts on its bone-facing surface. Features of these bone cuts, andoptionally features of corresponding resection cuts, can be optimized bya computer system based on patient-specific data. For example, the bonecut number and one or more bone cut planes, angles, or depths, as wellas the corresponding resection cut number and one or more resection cutplanes, angles, or depths, can be optimized, for example, to preservethe maximum amount of bone for each individual patient based on a seriesof two-dimensional images or a three -dimensional representation of thearticular anatomy and geometry and/or on a target limb alignment and/ordeformity correction. Optionally, one or more of the bone cut featuresand/or resection cut features can be adjusted by the operator.

The computer system also can construct the implant surfaces. Surfacesmay be composed of different elements. In certain embodiments, elementsof the surfaces can conform to the patient's anatomy. In thesesituations, the computer system can build a surface using the patient'sanatomical model, for example by constructing a surface that isidentical with or mostly parallel to the patient's anatomical surface.In certain embodiments, the computer system can use geometric elementssuch as arcs or planes to construct a surface. Transitions betweensurfaces can be smoothed using tapers or fillets. Additionally, thecomputer system may take into account constraints such as a minimum ormaximum threshold thickness or length or curvature of parts or featuresof the implant component when constructing the surfaces.

In another embodiment, the computer system can automatically orsemi-automatically add other features to the implant design. Forexample, the computer system can add pegs or anchors or other attachmentmechanisms. The system can place the features using anatomicallandmarks. Constraints can be used to restrict the placement of thefeatures. Examples of constraints for placement of pegs are the distancebetween pegs and from the pegs to the edge of the implant, the height ofthe pegs that results from their position on the implant, and forcingthe pegs to be located on the center line. Optionally, the system canallow the user to fine-tune the peg placement, with or without enforcingthe constraints.

5.4 Selecting and/or Designing an Implant Component

Using patient-specific features and feature measurements, and selectedparameters and parameter thresholds, an implant component, resection cutstrategy, and/or guide tool can be selected (e.g., from a library)and/or designed (e.g. virtually designed and manufactured) to have oneor more patient-adapted features. In certain embodiments, one or morefeatures of an implant component (and, optionally, one or more featuresof a resection cut strategy and/or guide tool) are selected for aparticular patient based on patient-specific data and desired parametertargets or thresholds. For example, an implant component or implantcomponent features can be selected from a virtual library of implantcomponents and/or component features to include one or morepatient-specific features and/or optimized features for a particularpatient. Alternatively or in addition, an implant component can beselected from an actual library of implant components to include one ormore patient-specific features and/or optimized features for theparticular patient.

In certain embodiments, one or more features of an implant component(and, optionally, one or more features of a resection cut strategyand/or guide tool) can be designed (e.g., designed and manufactured) toinclude one or more patient-specific features and/or optimized featuresfor a particular patient. In certain embodiments, one or more featuresof an implant component (and, optionally, one or more features of aresection cut strategy and/or guide tool) can be both selected anddesigned (e.g., designed and manufactured) to include one or morepatient-specific features and/or optimized features for the particularpatient. For example, an implant component having features that achievecertain parameter thresholds but having other features that do notachieve other parameter thresholds (e.g., a blank feature or a smalleror larger feature) can be selected, for example, from a library ofimplant components. The selected component then can be further designed(e.g. virtually designed and machined) to alter the blank or smaller orlarger feature to be achieve the selected parameter, for example, apatient-specific or patient-engineered feature or feature measurement.

An implant component can include one or more selected features and oneor more designed features. Alternatively or in addition, an implantcomponent can include one or more features that are selected anddesigned or altered to be patient-specific or patient -engineered.Moreover, an implant component can include any number of selected and/ordesigned features derived from any number of patient-specificmeasurements, including one or more of the exemplary measurementsdescribed above in Table 4. Depending on the clinical application asingle or any combination or all of the measurements described in Table4 and/or known in the art can be used. Additional patient-specificmeasurements and information that be used in the evaluation can include,for example, joint kinematic measurements, bone density measurements,bone porosity measurements, identification of damaged or deformedtissues or structures, and patient information, such as patient age,weight, gender, ethnicity, activity level, and overall health status.

The patient-specific measurements selected for the evaluation can beused to select and/or design any selected implant features, includingone or more of the exemplary features described in Table 1. The featurescan be selected and/or designed to be either patient-specific and/orpatient-engineered.

For example, one or more of an M-L measurement, an A-P measurement, andan S-I measurement of a patient's joint can be obtained from the subjectpreoperatively, for example, from one or more images of the subject'sjoint. Then, based on the one or more measurements, an implant orimplant component for the subject's joint can be selected and/ordesigned preoperatively to include an M-L, A-P, and/or S-I measurementthat is selected from a library to match the patient's M-L, A-P, and/orS-I measurement.

The process can include generating and/or using a model, for example, avirtual model, of the patient's joint that includes the selectedmeasurements and virtually fitting one or more selected and/or designedimplants into the virtual model. This approach allows for iterativeselection and/or design improvement and can include steps to virtuallyassess the fit, such as virtual kinematics assessment.

In another embodiment, the process of selecting an implant componentalso includes selecting one or more component features that optimizesfit with another implant component. In particular, for an implant thatincludes a first implant component and a second implant component thatengage, for example, at a joint interface, selection of the secondimplant component can include selecting a component having a surfacethat provides best fit to the engaging surface of the first implantcomponent. For example, for a knee implant that includes a femoralimplant component and a tibial implant component, one or both ofcomponents can be selected based, at least in part, on the fit of theouter, joint-facing surface with the outer-joint-facing surface of theother component. The fit assessment can include, for example, selectingone or both of the medial and lateral tibial grooves on the tibialcomponent and/or one or both of the medial and lateral condyles on thefemoral component that substantially negatively-matches the fit oroptimizes engagement in one or more dimensions, for example, in thecoronal and/or sagittal dimensions. For example, a surface shape of anon-metallic component that best matches the dimensions and shape of anopposing metallic or ceramic or other hard material suitable for animplant component. By performing this component matching, component wearcan be reduced.

For example, if a metal backed tibial component is used with apolyethylene insert or if an all polyethylene tibial component is used,the polyethylene will typically have one or two curved portionstypically designed to mate with the femoral component in a low frictionform. This mating can be optimized by selecting a polyethylene insertthat is optimized or achieves an optimal fit with regard to one or moreof: depth of the concavity, width of the concavity, length of theconcavity, radius or radii of curvature of the concavity, and/ordistance between two (e.g., medial and lateral) concavities. Forexample, the distance between a medial tibial concavity and a lateraltibial concavity can be selected so that it matches or approximates thedistance between a medial and a lateral implant condyle component.

Not only the distance between two concavities, but also the radius/radiiof curvature can be selected or designed so that it best matches theradius/radii of curvature on the femoral component. A medial and alateral femoral condyle and opposite tibial component(s) can have asingle radius of curvature in one or more dimensions, e.g., a coronalplane. They can also have multiple radii of curvature. The radius orradii of curvature on the medial condyle and/or lateral tibial componentcan be different from that/those on a lateral condyle and/or lateraltibial component.

Similar matching of polyethylene or other plastic shape to opposingmetal or ceramic component shape can be performed in the shoulder, e.g.with a glenoid component, or in a hip, e.g. with an acetabular cup, orin an ankle, e.g. with a talar component.

FIG. 27 is an illustrative flow chart showing exemplary steps taken by apractitioner in assessing a joint and selecting and/or designing asuitable replacement implant component. First, a practitioner obtains ameasurement of a target joint 2710. The step of obtaining a measurementcan be accomplished, for example, based on an image of the joint. Thisstep can be repeated 2711 as necessary to obtain a plurality ofmeasurements, for example, from one or more images of the patient'sjoint, in order to further refine the joint assessment process. Once thepractitioner has obtained the necessary measurements, the informationcan be used to generate a model representation of the target joint beingassessed 2730. This model representation can be in the form of atopographical map or image. The model representation of the joint can bein one, two, or three dimensions. It can include a virtual model and/ora physical model. More than one model can be created 2731, if desired.Either the original model, or a subsequently created model, or both canbe used.

After the model representation of the joint is generated 2730, thepractitioner optionally can generate a projected model representation ofthe target joint in a corrected condition 2740, e.g., based on aprevious image of the patient's joint when it was healthy, based on animage of the patient's contralateral healthy joint, based on a projectedimage of a surface that negatively-matches the opposing surface, or acombination thereof. This step can be repeated 2741, as necessary or asdesired. Using the difference between the topographical condition of thejoint and the projected image of the joint, the practitioner can thenselect a joint implant 2750 that is suitable to achieve the correctedjoint anatomy. As will be appreciated by those of skill in the art, theselection and/or design process 2750 can be repeated 2751 as often asdesired to achieve the desired result. Additionally, it is contemplatedthat a practitioner can obtain a measurement of a target joint 2710 byobtaining, for example, an x-ray, and then selects a suitable jointreplacement implant 2750.

One or more of these steps can be repeated reiteratively 2724, 2725,2726. Moreover, the practitioner can proceed directly from the step ofgenerating a model representation of the target joint 2730 to the stepof selecting a suitable joint implant component 2750. Additionally,following selection and/or design of the suitable joint implantcomponent 2750, the steps of obtaining measurement of a target joint2710, generating model representation of target joint 2730 andgenerating projected model 40, can be repeated in series or parallel asshown by the flow 2724, 2725, 2726.

5.5 Libraries

As described herein, implants of various sizes, shapes, curvatures andthicknesses with various types and locations and orientations and numberof bone cuts can be selected and/or designed and manufactured. Theimplant designs and/or implant components can be selected from,catalogued in, and/or stored in a library. The library can be a virtuallibrary of implants, or components, or component features that can becombined and/or altered to create a final implant. The library caninclude a catalogue of physical implant components. In certainembodiments, physical implant components can be identified and selectedusing the library. The library can include previously-generated implantcomponents having one or more patient-adapted features, and/orcomponents with standard or blank features that can be altered to bepatient-adapted. Accordingly, implants and/or implant features can beselected from the library.

FIGS. 28A to 28K show implant components with exemplary features thatcan be included in a library and selected based on patient-specific datato be patient-specific and/or patient engineered.

A virtual or physical implant component can be selected from the librarybased on similarity to prior or baseline parameter optimizations, suchas one or more of (1) deformity correction and limb alignment (2)maximum preservation of bone, cartilage, or ligaments, (3) preservationand/or optimization of other features of the patient's biology, such astrochlea and trochlear shape, (4) restoration and/or optimization ofjoint kinematics, and (5) restoration or optimization of joint-linelocation and/or joint gap width. Accordingly, one or more implantcomponent features, such as (a) component shape, external and/orinternal, (b) component size, and/or (c) component thickness, can bedetermined precisely and/or determined within a range from the libraryselection. Then, the selected implant component can be designed orengineered further to include one or more patient-specific features. Forexample, a joint can be assessed in a particular subject and apre-existing implant design having the closest shape and size andperformance characteristics can be selected from the library for furthermanipulation (e.g., shaping) and manufacturing prior to implantation.For a library including physical implant components, the selectedphysical component can be altered to include a patient-specific featureby adding material (e.g., laser sintering) and/or subtracting material(e.g., machining).

Accordingly, in certain embodiments an implant can include one or morefeatures designed patient-specifically and one or more features selectedfrom one or more library sources. For example, in designing an implantfor a total knee replacement comprising a femoral component and a tibialcomponent, one component can include one or more patient -specificfeatures and the other component can be selected from a library. Table 7includes an exemplary list of possible combinations.

TABLE 7 Illustrative Combinations of Patient-Specific andLibrary-Derived Components Implant Implant Implant component(s) havingcomponent(s) having component(s) a patient-specific feature a libraryderived feature Femoral, Tibial Femoral and Tibial Femoral and TibialFemoral, Tibial Femoral Femoral and Tibial Femoral, Tibial TibialFemoral and Tibial Femoral, Tibial Femoral and Tibial Femoral Femoral,Tibial Femoral and Tibial Tibial Femoral, Tibial Femoral and Tibial none

In certain embodiments, a library can be generated to include imagesfrom a particular patient at one or more ages prior to the time that thepatient needs a joint implant.

For example, a method can include identifying patients eliciting one ormore risk factors for a joint problem, such as low bone mineral densityscore, and collecting one or more images of the patient's joints into alibrary. In certain embodiments, all patients below a certain age, forexample, all patients below 40 years of age can be scanned to collectone or more images of the patient's joint. The images and data collectedfrom the patient can be banked or stored in a patient-specific database.For example, the articular shape of the patient's joint or joints can bestored in an electronic database until the time when the patient needsan implant. Then, the images and data in the patient-specific databasecan be accessed and a patient-specific and/or patient-engineered partialor total joint replacement implant using the patient's originallyanatomy, not affected by arthritic deformity yet, can be generated. Thisprocess results is a more functional and more anatomic implant.

5.6 Generating an Articular Repair System

The articular repair systems (e.g., resection cut strategy, guide tools,and implant components) described herein can be formed or selected toachieve various parameters including a near anatomic fit or match withthe surrounding or adjacent cartilage, subchondral bone, menisci and/orother tissue. The shape of the repair system can be based on theanalysis of an electronic image (e.g., MRI, CT, digital tomosynthesis,optical coherence tomography or the like). If the articular repairsystem is intended to replace an area of diseased cartilage or lostcartilage, the near anatomic fit can be achieved using a method thatprovides a virtual reconstruction of the shape of healthy cartilage inan electronic image.

In one embodiments, a near normal cartilage surface at the position ofthe cartilage defect can be reconstructed by interpolating the healthycartilage surface across the cartilage defect or area of diseasedcartilage. This can, for example, be achieved by describing the healthycartilage by means of a parametric surface (e.g. a B-spline surface),for which the control points are placed such that the parametric surfacefollows the contour of the healthy cartilage and bridges the cartilagedefect or area of diseased cartilage. The continuity properties of theparametric surface will provide a smooth integration of the part thatbridges the cartilage defect or area of diseased cartilage with thecontour of the surrounding healthy cartilage. The part of the parametricsurface over the area of the cartilage defect or area of diseasedcartilage can be used to determine the shape or part of the shape of thearticular repair system to match with the surrounding cartilage.

In another embodiment, a near normal cartilage surface at the positionof the cartilage defect or area of diseased cartilage can bereconstructed using morphological image processing. In a first step, thecartilage can be extracted from the electronic image using manual,semi-automated and/or automated segmentation techniques (e.g., manualtracing, region growing, live wire, model-based segmentation), resultingin a binary image. Defects in the cartilage appear as indentations thatcan be filled with a morphological closing operation performed in 2-D or3-D with an appropriately selected structuring element. The closingoperation is typically defined as a dilation followed by an erosion. Adilation operator sets the current pixel in the output image to 1 if atleast one pixel of the structuring element lies inside a region in thesource image. An erosion operator sets the current pixel in the outputimage to 1 if the whole structuring element lies inside a region in thesource image. The filling of the cartilage defect or area of diseasedcartilage creates a new surface over the area of the cartilage defect orarea of diseased cartilage that can be used to determine the shape orpart of the shape of the articular repair system to match with thesurrounding cartilage or subchondral bone.

As described above, the articular repair system can be formed orselected from a library or database of systems of various sizes,including various medio-lateral (ML) antero -posterior (AP) andsupero-inferior (SI) dimensions, curvatures and thicknesses, so that itachieves a near anatomic fit or match with the surrounding or adjacentcartilage, cortical bone, trabecular bone, subchondral bone, as well ascut bone, before or after preparing an implantation site. These systemscan be pre-made or made to order for an individual patient. In order tocontrol the fit or match of the articular repair system with thesurrounding or adjacent cartilage, cortical bone, trabecular bone,subchondral bone, as well as cut bone before or after preparing animplantation site or menisci and other tissues preoperatively, asoftware program can be used that projects the articular repair systemover the anatomic position where it will be implanted. Suitable softwareis commercially available and/or readily modified or designed by askilled programmer.

In yet another embodiment, the articular surface repair system can beprojected over the implantation site prior to, during or after planningor simulating the surgery virtually using one or more 3-D images. Thecartilage, cortical bone, trabecular bone, subchondral bone, as well ascut bone, before or after preparing an implantation site and otheranatomic structures are extracted from a 3-D electronic image such as anMRI or a CT using manual, semi-automated and/or automated segmentationtechniques. In select embodiments, segmentation is not necessary anddata are directly displayed using the grayscale image information.

Optionally, a 3-D representation of the cartilage, cortical bone,trabecular bone, subchondral bone, as well as cut bone, before or afterpreparing an implantation site and other anatomic structures as well asthe articular repair system is generated, for example using a polygon ornon-uniform rational B-spline (NURBS) surface or other parametricsurface representation. For a description of various parametric surfacerepresentations see, for example Foley, J. D. et al., Computer Graphics:Principles and Practice in C; Addison-Wesley, 2nd edition, 1995).

The 3D representations of the cartilage, cortical bone, trabecular bone,subchondral bone, as well as cut bone, before or after preparing animplantation site and other anatomic structures and the articular repairsystem can be merged into a common coordinate system. The articularrepair system can then be placed at the desired implantation site. Therepresentations of the cartilage, cortical bone, trabecular bone,subchondral bone, as well as cut bone, before or after preparing animplantation site, menisci and other anatomic structures and thearticular repair system are rendered into a 3-D image, for exampleapplication programming interfaces (APIs) OpenGL® (standard library ofadvanced 3-D graphics functions developed by SG), Inc.; available aspart of the drivers for PC-based video cards, for example fromwww.nvidia.com for NVIDIA video cards or www.3dlabs.com for 3Dlabsproducts, or as part of the system software for Unix workstations) orDirectX® (multimedia API for Microsoft Windows® based PC systems;available from www.microsoft.com). The 3-D image can be rendered showingthe cartilage, cortical bone, trabecular bone, subchondral bone, as wellas cut bone, before or after preparing an implantation site, menisci orother anatomic objects, and the articular repair system from varyingangles, e.g., by rotating or moving them interactively ornon-interactively, in real-time or non-real-time.

The software can be designed so that the articular repair system,including surgical tools and instruments with the best fit relative tothe cartilage, cortical bone, trabecular bone, subchondral bone, as wellas cut bone, before or after preparing an implantation site isautomatically selected, for example using some of the techniquesdescribed above. Alternatively, the operator can select an articularrepair system, including surgical tools and instruments and project itor drag it onto the implantation site using suitable tools andtechniques. The operator can move and rotate the articular repair systemin three dimensions relative to the implantation site, cut or uncut, andcan perform a visual inspection of the fit between the articular repairsystem and the implantation site, cut or uncut. The visual inspectioncan be computer assisted. The procedure can be repeated until asatisfactory fit has been achieved. The procedure can be performedmanually by the operator; or it can be computer assisted in whole orpart. For example, the software can select a first trial implant thatthe operator can test. The operator can evaluate the fit. The softwarecan be designed and used to highlight areas of poor alignment betweenthe implant and the surrounding cartilage or subchondral bone or meniscior other tissues. Based on this information, the software or theoperator can then select another implant and test its alignment. One ofskill in the art will readily be able to select, modify and/or createsuitable computer programs for the purposes described herein.

In another embodiment, the implantation site can be visualized using oneor more cross-sectional 2D images. Typically, a series of 2Dcross-sectional images will be used. The 2D images can be generated withimaging tests such as CT, MRI, digital tomosynthesis, ultrasound, oroptical coherence tomography using methods and tools known to those ofskill in the art. The articular repair system can then be superimposedonto one or more of these 2-D images. The 2-D cross-sectional images canbe reconstructed in other planes, e.g., from sagittal to coronal, etc.Isotropic data sets (e.g., data sets where the slice thickness is thesame or nearly the same as the in-plane resolution) or near isotropicdata sets can also be used. Multiple planes can be displayedsimultaneously, for example using a split screen display. The operatorcan also scroll through the 2D images in any desired orientation inreal-time or near-real-time; the operator can rotate the imaged tissuevolume while doing this. The articular repair system can be displayed incross-section utilizing different display planes, e.g., sagittal,coronal or axial, typically matching those of the 2-D imagesdemonstrating the cartilage, cortical bone, trabecular bone, subchondralbone, as well as cut bone, before or after preparing an implantationsite, menisci or other tissue. Alternatively or in addition, athree-dimensional display can be used for the articular repair system.The 2D electronic image and the 2D or 3-D representation of thearticular repair system can be merged into a common coordinate system.The articular repair system can then be placed at the desiredimplantation site. The series of 2D cross-sections of the anatomicstructures, the implantation site and the articular repair system can bedisplayed interactively (e.g., the operator can scroll through a seriesof slices) or noninteractively (e.g., as an animation that moves throughthe series of slices), in real-time or non-real-time.

In another embodiment, the fit between the implant and the implantationsite is evaluated. The implant can be available in a range of differentdimensions, sizes, shapes and thicknesses. Different dimensions, sizes,shapes and thicknesses can be available for a medial condyle, a lateralcondyle, a trochlea, a medial tibia, a lateral tibia, the entire tibia,a medial patella, a lateral patella an entire patella, a medialtrochlea, a central trochlea, a lateral trochlea, a portion of a femoralhead, an entire femoral head, a portion of an acetabulum, an entireacetabulum, a portion of a glenoid, an entire glenoid, a portion of ahumeral head, an entire humeral head, a portion of an ankle joint anentire ankle joint, a portion or an entire elbow, wrist, hand, finger,spine, facet joint.

In certain embodiment, a combination of parameters can be selected. Forexample, one or more of an M-L measurement, an A-P measurement, and anS-I measurement a patient's joint can be obtained from the subjectpreoperatively, for example, from one or more images of the subject'sjoint. Then, based on the one or measurements, an implant or implantcomponent for the subject's joint can be designed or selectedpreoperatively.

6. Designing and/or Selecting a Femoral Implant Component

The following subsections describe aspects of certain embodiments ofmodels, implant designs, implants, and implant components related to aknee replacement. While the sections particularly describe embodimentsof total knee implants, it is understood that the teachings areapplicable to other embodiments including, but not limited to,unicompartmental knee implants, bicompartmental knee implants, and otherarticular implants such as shoulder implants, hip implants, and spinalfacet implants.

6.1 Femoral Implant Component

A traditional femoral implant component used in a primary total kneearthroplasty (“TKA”) includes: an outer, joint-facing surface (i.e.,inferior surface) having a standard topography; an inner, bone-facingsurface (i.e., superior surface) that includes five standard bone cuts;and a standard implant thickness between the joint-facing surface andthe bone-facing surface. FIG. 29 shows a coronal view of a patient'sfemoral bone 2900 and (in dashed lines) the five standard resection cutsused to remove portions of the subject's distal femur in order to fitthe traditional femoral implant component. As shown by the dashed linesin the figure, a traditional resection performed in a TKA includes ahorizontal resection cut 2910, an anterior resection cut 2920, aposterior resection cut 2930, an anterior chamfer resection cut 2940,and a posterior chamfer resection cut 2950. The anterior and posteriorresection cuts 2920, 2930 typically are placed in a substantiallycoronal plane. With a traditional implant, the five standard resectioncuts are performed so that the patient's distal femur approximatelynegatively-matches the standard five bone cuts on the inner, bone-facingsurface of the traditional femoral implant component. In other words,the patient's bone is resected to fit the shape of the traditionalfemoral implant component.

Dissimilarly, in various embodiments described herein, one or morefeatures of an implant component and/or implant procedure are designedand/or selected to provide a patient-adapted implant component. Forexample, in certain embodiments, one or more features of an implantcomponent and/or implant procedure are designed and/or selectedpreoperatively, based on patient-specific data, to substantially match(e.g., substantially negatively-match and/or substantiallypositively-match) one or more of the patient's biological structures ora predetermined percentage thereof. For example, in certain embodiments,a femoral implant component can include an outer, joint-facing surface(i.e., inferior surface) having a sagittal or j-curve on one or bothcondyles that, at least in part, positively-matches the correspondingbone or cartilage curvature on the patient's uncut femur. Thispatient-specific implant component feature can be preoperativelyselected and/or designed based on the patient's joint dimensions asseen, for example, on a series of two -dimensional images or athree-dimensional representation generated, for example, from a CT scanor MRI scan.

Alternatively or in addition, one or more features of an implantcomponent and/or implant procedure can be preoperatively derived frompatient-specific data to provide a patient-engineered feature, forexample, to optimize one or more parameters, such as one or more of theparameters described above. For example, in certain embodiments, a bonepreserving femoral implant component can include an inner, bone-facingsurface (i.e., superior surface) having one or bone cuts that, at leastin part, are patient-derived, optionally together with matchingpatient-derived resection cuts, to minimize the amount of resected bone(and maximize the amount of retained bone), for example, on thepatient's femur. This patient-engineered implant component feature canbe preoperatively selected and/or designed based on the patient's jointdimensions as seen, for example, on a series of two-dimensional imagesor a three-dimensional representation generated, for example, from a CTscan or MRI scan.

In certain embodiments, the size of an implant component can be designedand/or selected to substantially match the size of a patient'scorresponding biological structure or a predetermined percentagethereof. For example, the ML and/or AP and/or proximal-distal dimensionsof one or more sections of a femoral implant component can bepreoperatively designed and/or selected to substantially match thecorresponding dimension(s) of a patient's distal femur as determined,for example, from one or more images of the patient's joint. In certainembodiments, the size of the femoral implant component can be designedand/or selected based on one or more patient-specific dimensions, suchas the length of the patient's epicondylar axis, which can be determinedfrom preoperatively collected patient data, such as image data.

In certain embodiments, an area measurement on the implant component canbe designed and/or selected preoperatively to match, in whole or inpart, a corresponding area measurement on the patient's femur or apredetermined percentage thereof. For example, as shown in FIGS. 30A and30B, the surface area of all or part of the bone-facing surface of theimplant component can be designed and/or selected from patient-specificdata, in conjunction with a preoperatively designed resection strategy,to substantially match the corresponding resected surface area of thepatient's femur. As shown in the figures, the surface area of theimplant component is a close fit to the resected surface area. Incertain embodiments, the implant component substantially covers theresected surface area, for example, by covering up to 100% and at least90%, greater than 90%, at least 95%, greater than 95%, at least 97%,greater than 97%, at least 98%, greater than 98%, at least 99%, and/orgreater than 99% of the resected surface area of the patient's distalfemur.

In certain embodiments, the thickness of one or portions of an implantcomponent can be designed and/or selected to match the correspondingdimension of the patient's biological structure. For example, theimplant component thickness can be designed and/or selected tosubstantially match in one or more sections the thickness of thepatient's cartilage, the thickness of the patient's resected bone, thetotal thickness of the patient's cartilage and resected bone, or anoptimized thickness based on one or more of the parameters describedabove. In certain embodiments, the additive thickness of two or moreimplant components, for example, femoral and tibial implant components,can be designed and/or selected together to substantially match in oneor more sections the patient's joint-gap distance, for example, thedistance between the patient's femoral and tibial bone surfaces, uncutor resected.

As will be appreciated by those of skill in the art, the thickness ofany implant component described herein can vary between differentlocations across its surface depending upon the patient's anatomy and/orthe depth of the damage to the cartilage and/or bone to be corrected atany particular location on the patient's articular surface.

In certain embodiments, the implant component design and/or selectioncan include a thickness, a minimum implant thickness, and/or a maximumimplant thickness that is engineered from patient-specific data toprovide to the patient an optimized implant fit with respect to one ormore parameters. Moreover, the additive thickness of two or more implantcomponents can be engineered from patient-specific data to optimize theimplant thickness for meeting one or more of the parameters describedabove. For example, the femoral and/or tibial implant thicknesses can beengineered from patient-specific data to optimize or correct thepatient's joint-gap distance. The patient-specific data that may be usedto engineer a minimum implant thickness can include, for example, one ormore of patient height, patient weight, patient age, patient activitylevel, patient joint-size (e.g., epicondylar distance or condylarwidth), and other patient-specific data.

In preferred embodiments, the minimum implant component thickness can beengineered based on, or together with, other patient-engineereddimensions or features of the implant component, for example, one ormore of implant component size, implant component condyle width, and oneor more implant component surface curvatures. For example, as shown inFIG. 31A, the thinnest part of a femoral implant component frequentlyappears at the intersection of the implant component's distal bone cutand a posterior bone cut 3100. This portion of an implant component alsofrequently shows the highest stress load, as exemplified by the FEAanalysis results shown in FIG. 31B. Accordingly, the minimum implantcomponent thickness for this or any portion of the implant component canbe engineered based on one or more factors related to stress load, forexample: the size of the patient; the size of the patient's femur; thesize of the patient's condyle; the size of the patient-engineeredimplant component; the size of the implant component condyle; and theimplant component's joint-facing surface curvature in the region that isopposite the intersection of the distal bone cut and posterior bone cut.In this way, a patient-specific minimum implant thickness can beengineered from patient-specific data, such as image data, and designedinto the patient-adapted implant. This allows for minimal bone to beresected in the implant procedure and thereby can help to maximize bonepreservation for any particular patient. Preservation of bone can allowfor a subsequent knee implant to be a primary knee implant procedure,rather than a revision procedure.

In addition or alternatively, the implant component can be designed toinclude a standard minimum thickness and/or a standard maximum thicknessin one or more locations. For example, in certain embodiments, theimplant component can include a minimum implant thickness of 9 mm, lessthan 9 mm, 8 mm, less than 8 mm, 7 mm, less than 7 mm, 6 mm, less than 6mm, 5 mm, and/or less than 5 mm.

In certain embodiments, both medial and lateral condyles include thesame minimum implant thickness.

In certain embodiments, the joint-facing surface of a femoral implantcomponent includes one or more patient-specific dimensions thatpositively or negatively-match the patient's biological structure orthat are engineered from patient-specific data to provide to the patientan optimized implant fit with respect to one or more parameters, forexample, as described above. For example, a femoral implant componentcan be designed and/or selected to include a joint-facing surface thatsubstantially positively-matches one or more dimensions of the patient'sfemoral joint-facing surface, for example, as determined bypreoperatively collected data, such as image data. The patient's femoraljoint-facing surface that is included in the image data can include, forexample, one or more of the cartilage surface and the bone surface ofthe patient's femur.

The joint-facing surface of a femoral implant component includes bearingsurfaces that contact one or more opposing surfaces during proper jointfunction. In a total knee implant, the bearing surfaces include one ormore portions of the medial and lateral condyles of the femoralcomponent and also the corresponding surfaces on the tibial component.Bearing surfaces also can include the trochlear area of a femoralimplant component and the corresponding surface of a patella or patellaimplant component. In certain embodiments, the femoral implant componentcan be designed and/or selected to include a joint-facing surface thatsubstantially negatively-matches one or more dimensions of an opposingsurface, such as a tibial surface or a patellar surface, of thepatient's biological structure or of another implant component, such asa tibial implant component or a patellar implant component.

The primary load bearing surfaces of the femoral implant componentinclude the joint-facing surfaces of the medial and lateral femoralcondyles. In particular, these condylar surfaces engage the tibia or atibial implant component during knee joint motion. Accordingly, thedesign of these condyles can affect various parameters; for example, asdescribed above, such as kinematics and implant wear, particularly theproper motion of the implant at the joint.

In certain embodiments, one or more dimensions or features of one orboth implant component condyles is designed and/or selectedpreoperatively to be patient-specific (e.g., to substantially match thepatient's condyle or condyles in one or more dimensions or features). Inaddition or alternatively, one or more dimensions or features of one orboth implant component condyles can be designed and/or selectedpreoperatively to be patient -engineered (e.g., engineered frompatient-specific data to provide to the patient and optimized fit). Thepatient-specific data used to design and/or select the patient-adapted(e.g., patient -specific or patient-engineered) dimensions or featurescan include one or more images of, at least in part, one or both of thepatient's femoral condyles. Accordingly, the manufactured femoralimplant component generated from this design and/or selection includes acondyle having one or more patient-adapted dimensions or features.

The one or more patient-adapted dimensions or features of one or bothcondyles can include, for example, width in one or more locations,height in one or more locations, intercondylar distance in one or morelocations, and one or more curvatures of at least a portion of thejoint-facing surface of the condyle. The curvatures can include, forexample, one or more of a sagittal curvature on the medial condyle, acoronal curvature on the lateral condyle, a sagittal curvature on thelateral condyle and a coronal curvature on the lateral condyle. Thedimensions or features on the medial and lateral condyles of the implantcomponent can be designed and/or selected independently of thecorresponding dimensions on the other condyle, provided thatpatient-specific data (e.g., image data) is available for theappropriate condyle.

Any implant component dimensions or features that are notpatient-adapted can have a standard dimension or feature. In addition,an implant design can include applying a standard dimension or featureif patient-specific data exceeds or fails to meet a certain thresholdvalue. For example, in certain embodiments, intercondylar distance canbe patient -specific; however, if the patient-specific data shows thatthe patient's intercondylar distance does not exceed a minimumintercondylar distance, such as 40 mm, a standard intercondylar distanceof 40 mm can be included in the femoral implant component.

In certain embodiments, one or more of the condylar width, area, andheight of an implant component can be designed and/or selectedpreoperatively to be patient-adapted in one or more locations along oneor both condyles.

For example, the width of one or both implant component condyles can bedesigned and/or selected from patient-specific data to substantiallymatch the corresponding width of the patient's resected condyle surface.Similarly, the two-dimensional area of a portion of the bone-facingsurface of one or both implant component condyles can be designed and/orselected from patient-specific data to substantially match thecorresponding area of the patient's resected condyle. In this way, theimplant component can include one or both condyles that, at least inpart, substantially covers the width and/or area of resected bonesurface on the condyle, for example, by covering up to 100% and at least90%; greater than 90%; at least 95%; greater than 95%; at least 97%;greater than 97%; at least 98%; greater than 98%; at least 99%; and/orgreater than 99% of the width and/or area of the patient's resectedcondyle surface.

In addition or alternatively, the height of a portion of one or bothimplant component condyles can be designed and/or selected frompatient-specific data to substantially match the corresponding height ofthe patient's condyle, for example, the height of the correspondingresected portion of the patients' condyle.

In certain embodiments, one or both of the intercondylar distance andthe intercondylar angle of the implant component can be designed and/orselected preoperatively to be patient-specific in one or more locations.For example, the distance and/or angle between the implant componentcondyles can be designed and/or selected from patient-specific data tosubstantially match the corresponding distance and/or angle of thepatient's condyles at one or more locations.

The intercondylar distance can be measured from any point on the medialcondyle to any point on the lateral condyle. For example, theintercondylar distance can be measured as the distance between theoutside edges of the condyles (e.g., from the medial edge of the medialcondyle to lateral edge of the lateral condyle), as the distance betweenthe inside edges of the condyles (e.g., from the lateral edge of themedial condyle to the medial edge of the lateral condyle), or as thedistance from the sagittal crest of the medial condyle (i.e., theJ-curve of the medial condyle) to the sagittal crest of the lateralcondyle (i.e., the J-curve of the lateral condyle).

The intercondylar angle can be measured as the angle between a line onthe medial condyle and a line on the lateral condyle. For example, theintercondylar angle can be measured as the angle between a tangent lineto any point on the medial condyle and a tangent line to any point onthe lateral condyle. One or each tangent line can be defined by a pointon the outside edge of a respective condyle, by a point on the insideedge of a respective condyle, or by a point on the J-curve of arespective condyle. Alternatively, one or both lines used to measure theangle can be defined by any two or more points on the same condyle,rather than as a tangent line. In particular, in certain embodiments,the implant component includes a patient-adapted (e.g., patient-specificor patient-adapted) intercondylar angle at the trochlear notch.

In certain embodiments, the joint-facing surface of a femoral implantcomponent can be designed and/or selected to include one or more of apatient-specific curvature, at least in part, a patient-engineeredcurvature, at least in part, and a standard curvature, at least in part.Various exemplary combinations of implant components havingpatient-adapted (e.g., patient-specific or patient-engineered) andstandard coronal and sagittal condylar curvatures are shown in Table 8.

TABLE 8 Exemplary combinations of patient-adapted and standard condylarcurvatures for a femoral implant component Group Medial condyle Medialcondyle Lateral condyle Lateral condyle description coronal curvaturesagittal curvature coronal curvature sagittal curvature All standardstandard standard standard standard curvatures 1 patient-patient-adapted standard standard standard adapted standardpatient-adapted standard standard curvature, standard standardpatient-adapted standard at least in standard standard standardpatient-adapted part 2 patient- patient-adapted patient-adapted standardstandard adapted patient-adapted standard patient-adapted standardcurvatures, patient-adapted standard standard patient-adapted at leastin standard patient-adapted patient-adapted standard part standardpatient-adapted standard patient-adapted standard patient-adaptedstandard patient-adapted standard standard patient-adaptedpatient-adapted 3 patient- patient-adapted patient-adaptedpatient-adapted standard adapted patient-adapted patient-adaptedstandard patient-adapted curvatures, patient-adapted standardpatient-adapted patient-adapted at least in standard patient-adaptedpatient-adapted patient-adapted part 4 patient- patient-adaptedpatient-adapted patient-adapted patient-adapted adapted curvatures, atleast in part

In certain embodiments, the joint-facing surface of the femoral implantcomponent can be designed and/or selected to include a patient-specificcurvature, at least in part. For example, any one or more of a coronalcurvature of the medial condyle, a sagittal curvature of the medialcondyle, a coronal curvature of the lateral condyle, and a sagittalcurvature of the lateral condyle can be designed and/or selectedpreoperatively to substantially match the patient's correspondingcurvature, e.g., subchondral bone or cartilage, at least in part, or canbe derived from the patient's corresponding curvature, e.g. ofsubchondral bone or cartilage, at least in part.

In certain embodiments, the load-bearing portion of one or both implantcondyles that contacts the tibial plateau during a normal range ofmotion (e.g., from the distal portion to the posterior portion of theimplant component's joint-facing condyle surfaces) can be designedand/or selected to include one or more patient-specific curvatures.FIGS. 32A and 32B show exemplary load bearing surfaces of a femur incoronal view (FIG. 32A) and in sagittal view (FIG. 32B). As indicated bythe figures, the load bearing surface on each of the medial and lateralcondyles includes a coronal curvature 3210 and a sagittal curvature3220. Non-patient-specific curvatures can include standard curvatures(e.g., selected from a family of standard curvatures, for example, afamily of 3, 4, 5, 6, 7, or more standard curvatures) and/or engineeredcurvatures (e.g., engineered from patient-specific data to optimize oneor more parameters, for example, as described above). For example, afemoral implant component can include a medial condyle having apatient-specific sagittal curvature, at least in part, and a standardcoronal curvature; and a lateral condyle having standard coronal andsagittal curvatures.

In certain embodiments, the joint-facing surface of a femoral implantcomponent can be designed and/or selected to include, at least in part,a patient-engineered curvature. For example, the joint-facing surfacecan be designed and/or selected to include a patient-engineeredcurvature, at least in part, for any one or more of a medial condylecoronal curvature, a medial condyle sagittal curvature, a lateralcondyle coronal curvature, and a lateral condyle sagittal curvature. Incertain embodiments, one or more load-bearing portions of the condylarsagittal and/or coronal curvature is designed and/or selected to bepatient -engineered. Non-patient-engineered curvatures can includestandard curvatures and/or patient-specific curvatures.

In certain embodiments, an implant component curvature can bepreoperatively engineered based on patient-specific data to correct oroptimize the patient's condyle curvature. The procedure can use a modelor a mathematical formula to engineer a corrected or optimized condylecurvature and/or shape. The model or mathematical formula can be basedon one or more patient-specific dimensions. For example, in certainembodiments, the implant component can include one or more curvaturesthat have been smoothed to address, minor imperfections in the patient'scorresponding curvature. In certain embodiments, one condyle can beengineered to have a curvature relative to the corresponding curvaturein the patient's other condyle. For example, an implant component can beengineered to have a lateral sagittal J-curve engineered based on thepatient's medial sagittal J-curve. The lateral J-curve can be engineeredto have one or more radii of curvature that are shorter, for example,5%, 10%, 15%, 20%, 10-15%, and/or 0-20% shorter, than the correspondingradii of curvature of the patient's medial J-curve. In certainembodiments, the implant component can be designed to have a lateralJ-curve shape that substantially positively-matches the patient's medialJ-curve shape.

In patients in need of knee replacement, the lateral condyle issometimes deformed or hypoplastic, which can contribute to a valgusdeformity. In fact, hypoplastic lateral condyles may be present in 20%of patients that require knee replacement. An implant that is engineeredfrom patient-specific data to address this deformity, by correcting oroptimizing the lateral condyle, can include one or more expandedcurvatures in one or more locations on the lateral condyle, relative tothe patient's corresponding uncut medial or lateral condyle.Accordingly, the implant is engineered to include additional material onthe outer, joint-facing surface of the implant component's lateralcondyle. The expanded curvature(s) and/or material on the outside of thecondyle can be used to design a material savings on the inside of thecorresponding section of the implant component, for example, bymaintaining a minimum material/implant thickness from the outside(joint-facing surface) to the inside (bone-facing surface) of theimplant component. In this way, by adding material to the externalcontour of the implant component and maintaining a minimum materialthickness of the implant component, bone preservation can be maximized.Specifically, with more material on the joint-facing surface of theimplant and less material on the inner, bone-facing surface of theimplant, the resection cuts are made closer to the surface of the bone.Accordingly, this approach uses the patient-adapted design of theimplant component to both correct a condyle shape abnormality, such as alateral condyle abnormality, such as hypoplasia, and to maximize bonepreservation.

In certain embodiments, one or more curvatures on one or both condylescan be engineered from patient-specific data, for example, in order tooptimize joint kinematics. For example, the medial condyle in thetrochlear region of the implant component can be engineered to be 5 mmlateral relative to the patient's condyle, which can help lateralize thepatella.

Different curvatures can be selected on the medial condyle and thelateral condyle of an implant component. Moreover, one or morecurvatures of one condyle can be patient-specific, in whole or in part,while one or more curvatures on the same condyle or on the other condylecan be patient-engineered, in whole or in part, or standard, in whole orin part.

The one or more patient-adapted (i.e., patient-specific orpatient-engineered) curvatures and standard curvatures on thejoint-facing surface of a femoral implant component can be combined in acondyle to take on any overall shape. FIGS. 33A through 33F illustrateexemplary types of curvatures 3300, 3310, 3320, 3330, 3340 for one ormore condylar coronal or sagittal curvatures. An implant componentcondyle can include a surface curvature corresponding to a section ofany one or more geometric shapes, such as a circle, a parabola, ahyperbola, an ellipsoid, and any other geometric shape, optionallystandard or patient-adapted or patient-derived. The curvature also caninclude, in part, a substantially straight line portion, as illustratedby the curvature 3350 in FIG. 33F. Different portions of a condyle, suchas the anterior portion, the distal portion, the posterior portion, theload-bearing portion, and/or the non-load-bearing portion, each caninclude a different curvature than one or more other portions, in asagittal plane or in a coronal plane or in an axial plane in a trochlea,for example. For example, in certain embodiments the loadbearing-portion of the medial condyle can include a different curvaturethan the non-load-bearing portions of the same condyle and optionally,than any or all sections of the lateral condyle. Similarly, in certainembodiments the load bearing-portion of the lateral condyle can includea different curvature than the non-load-bearing portions of the samecondyle and optionally, than any or all sections of the medial condyle.These curvature features also can apply to the curved portion on one orboth of the lateral and medial surfaces of the proximal tibia thatengage the lateral and medial femoral condyles during normal motion.

The curvature 3300 in FIG. 33A corresponds to a section of a circle,and, accordingly, can be defined by a single radius of curvature acrossits entire curvature. Two exemplary radii of curvature are shown asdotted lines in FIG. 33A. However, the curvatures 3310, 3320, 3330, 3340in FIGS. 33B through 33E each correspond to a section of a non-circulargeometric shape and therefore each include radii having differentlengths across their curvatures. Moreover, the straight line portion ofthe curvature 3350 illustrated in FIG. 33F includes no radius ofcurvature. Accordingly, as exemplified by the circular curvature 3300shown in FIG. 33A, a curvature or a portion of a curvature of an implantcomponent, for example, a condylar coronal or sagittal curvature on thejoint-facing surface of a femoral implant component can include a singleradius of curvature. Alternatively or in addition, as exemplified by thenon-circular curvatures 3310, 3320, 3330, 3340 shown in FIGS. 33Bthrough 33F, a curvature or a portion of a curvature of an implantcomponent, for example, a condylar coronal or sagittal curvature on thejoint-facing surface of a femoral implant component, can includemultiple radii of curvature and, optionally, no radii of curvature(e.g., for a straight line portion of a curvature).

Moreover, in certain embodiments, a curvature or a portion of acurvature of an implant component, for example, a condylar coronal orsagittal curvature on the joint-facing surface of a femoral implant,component can include a combination of patient-specific radii ofcurvature, patient-engineered radii of curvature, and/or standard radiiof curvature. In other words, a curvature can include a portion that ispatient-specific, a portion that is patient -engineered, and/or aportion that is standard. These can be present in the same plane ordimension, e.g., a sagittal dimension, a coronal dimension or an axialdimension, or these can be present in different dimensions. For example,at least a portion of a sagittal curvature of the implant can bepatient-specific or patient-engineered, while at least a portion of acoronal curvature can be standard or constant patient-engineered. Forexample, FIGS. 34A and 34B illustrate a design for a femoral implantcomponent having a J-curve that is patient-specific in part andpatient-engineered in part. Specifically, as shown in the figure, theJ-curve is designed to be patient-specific except for a distal portionand a posterior portion of the curvature. In the distal portion, theJ-curve is smoothed relative to the patient's J-curve. In the posteriorportion, the J-curve is tapered out 1-2 mm relative to the patient'sJ-curve.

FIGS. 35A and 35B illustrate two femoral implant components, one havinga J-curve that is substantially patient-specific and one having aJ-curve that is partially patient-specific and partiallypatient-engineered. Specifically, both implant components shown on theright side of the figure were designed based on patient-specific data.However, the top implant component includes a J-curve that, at least inits load-bearing portion, substantially positively-matches the patient'sJ-curve. The bottom implant component includes a J-curve that wasengineered in region 3510 to diverge from the patient-specific J-curve.These engineered alterations from a patient's existing J-curve can beemployed for example, to match or approximate the height of thepatient's existing or missing cartilage, to correct an abnormality inthe patient's existing J-curve (e.g., arthritic flattening of thecondyle, subchondral cysts, or osteophyte formation), to match one ormore features of a corresponding implant component (e.g., a tibialimplant component), and/or to optimize the patient's biomechanics or oneor more other parameters determined by a clinician or operator to beimportant.

One or more radii of a condylar curvature of a femoral implant componentcan be engineered from patient-data to optimize or correct any one ormore parameters, for example, any one or more parameters describedabove. For example, with reference to FIGS. 35A and 35B, the distalload-bearing portion of the J-curve frequently has the flattest surface3520. In certain embodiments, this portion of the J-curve can beengineered to shift the flattest portion anteriorly or posteriorly tocorrect or optimize the patient's biomechanics, joint alignment, implantload pattern, and/or implant wear pattern. In FIGS. 35A and 35B, theflattest portion 3520 of the J-curve in the top implant componentappears at the distal portion of the implant. However, the bottomimplant is engineered to include the flattest portion 3530 of theJ-curve further posterior to the distal position. In certainembodiments, an implant component's entire condylar sagittal curvaturecan be flexed (e.g., rotated anteriorly or posteriorly, for example,about the femoral mechanical axis or the sagittal axis) in an implantrelative to the patient's corresponding curvature, in order to corrector optimize the patient's biomechanics and/or alignment.

In certain preferred embodiments, the femoral implant component ispreoperatively designed and/or selected to include one or both condylar,bearing surfaces having a sagittal curvature (e.g., a J-curve) that, atleast in part, substantially positively -matches or is derived from thecorresponding sagittal curvature of the patient's condyle, e.g. portionsof cartilage or subchondral bone or combinations thereof, as determinedfrom patient -specific data including, for example, image data. Inaddition, the coronal curvature of the implant component can include astandard curvature, for example, selected by choosing from among afamily of 5, 6, 7, 8, 9, or 10 implants or implant blanks the one thatincludes a coronal curvature that is most similar to the patient'scoronal curvature in one or more locations on the curvature.Alternatively, an implant component condyle curvature can be selected bychoosing from among a family of implants or implant blanks the one that,as compared to the patient's curvature, includes longer and/or shorterradii of curvature at a load-bearing portion of the curvature, in orderto achieve a less constraining or a more constraining biomechanicalsituation during knee motion. FIG. 36 illustrates the use of a coronalcurvature having a longer radius of curvature (e.g., 40 mm radius ofcurvature) versus a coronal curvature having shorter radius of curvature(e.g., 20 mm radius of curvature).

The radii of curvature of a human femoral condyle coronal curvaturetypically range from 20 to 30 mm. In certain embodiments, one or bothfemoral implant component condyles and/or the corresponding curvature ofthe bearing surface on the tibial implant component, include a coronalcurvature that matches a particular patient's coronal curvature. Incertain embodiments, one or both femoral implant component condylesand/or the corresponding curvature of the bearing surface on the tibialimplant component, include a standard coronal curvature within the rangeof typical human coronal curvatures, for example, from about 20 mm toabout 30 mm. In certain embodiments, one or both femoral implantcomponent condyles and/or the corresponding curvature of the bearingsurface on the tibial implant component, include a standard coronalcurvature outside of the range of typical human coronal curvatures, forexample, less than 20 mm, about 15 mm, less than 15 mm, greater than 30mm, 35 mm, greater than 35 mm, between about 30 mm and about 40 mm, 40mm, and/or greater than 40 mm. The tibial implant component can bedesigned to match or reflect at least one of a sagittal femoralcurvature or a coronal femoral curvature. The corresponding radii on thetibial implant component can be applied or derived from the femur in aratio, e.g., 1:1, 1:2, 1:3, 1:4, 1:5, 1:8, 1:10, 1:15, 1:20, in at leastone of a sagittal dimension or a coronal dimension, or combinationsthereof, medially only, laterally only, or both. For example, in certainembodiments, at least a portion of the femoral implant's coronalcurvature (e.g., the center portion of the condyle) and/or thecorresponding portion of the tibial implant component curvature cancorrespond to a section of a circle having a radius of curvature lessthan 20 mm, less than 15 mm, 15 mm, greater than 30 mm, 35 mm, greaterthan 35 mm, 40 mm, and/or greater than 40 mm.

Using longer radii of curvature (e.g., greater than 30 mm, 35 mm,greater than 35 mm, 40 mm, and/or 40 mm) for a femoral implant'scondylar coronal curvature can provide certain advantages. For example,FIGS. 37A and 37B show coronal cross-sections of two femoral implantcomponent condyles. As shown, each condyle includes an outer,joint-facing surface coronal curvature having a constant radius ofcurvature, at least in part (depicted as radius R1 and radius R2,respectively). In addition, as shown, the two condyles have the samemaximum component thickness (with the condyle in FIG. 37A having alonger radius of curvature than the condyle in FIG. 37B). As can be seenfrom a comparison of figures, where the width and maximum componentthickness are the same for the two components, the component with thelonger radius of curvature allows for more material at the edge of thecomponent, and therefore can be less likely to fail in this area of thefemoral implant component. In certain embodiments, the one or morecondylar curvatures, e.g., one or more coronal curvatures and/orsagittal curvatures, and/or component width, can be engineered frompatient-specific data to be as close to the patient-specific curvatureand/or width as possible after a threshold minimum thickness and/orminimum edge thickness or minimum chamfer cut thickness is achieved. Forexample, a threshold minimum thickness and/or minimum edge thicknessand/or minimum chamfer cut thickness can be set initially (e.g.,predetermined). Material properties of the implant component and/orloading conditions or biomechanical modeling including finite elementmodeling can assist in determining the threshold minimum thicknessand/or minimum edge thickness. Subsequently, one or morepatient-specific curvatures or widths or shapes are derived, for exampleby determining the curvature or width or shape of subchondral bone orcartilage. These curvatures can be used to derive a shape or curvatureor width of one or more bearing surfaces of the implant component, e.g.,in a coronal plane, sagittal plane or axial plane. The shape orcurvature or width of the one or more bearing surfaces of the implantcomponent then can be altered in order to achieve the predeterminedminimum thickness or minimum edge thickness or minimum chamfer cutthickness criterion. This alteration can be performed using computerizedmethods as well as manual, e.g., operator selected, methods.

Similarly, a maximum thickness, and/or maximum edge thickness and/ormaximum chamfer cut thickness and/or maximum bone-cut thickness can bepredetermined. The shape or curvature or width of the one or morebearing surfaces of the implant then can be altered in order to achievethe predetermined maximum thickness and/or maximum edge thickness and/ormaximum chamfer cut thickness and/or maximum bone cut thicknesscriterion. By optimizing against a maximum bone-cut thickness, theimplant can be selected or designed so that it is sufficiently bonepreserving to be a pre-primary implant, e.g., where, for example, adistal bone cut is distal to the bone cut with a standard of the shelffemoral component implant, thereby enabling later revision to a standardtotal knee system.

Various dimensions and features of a patient's condyles, such as width,area, height, intercondylar distance, intercondylar angle, and surfacecontour and curvatures, e.g., of the patient's cartilage or subchondralbone or combinations thereof, including normal or diseased cartilage,can be determined from one or more images of the patient's knee joint.In certain embodiments, a dimension or feature of the patient's condylescan be assessed to include cartilage on the patient's distal femur. Incertain embodiments, a dimension or feature can be assessed based on thepatient's bone, for example, subchondral bone, on the patient's distalfemur. If subchondral bone is used to assess the patient's condylarcurvature, optionally a standard cartilage thickness (e.g., 2 mm), or anapproximate cartilage thickness derived from patient-specific data(e.g., age, joint-size, contralateral joint measurements, and/or otherdata), can be used as part of the preoperative implant design, forexample, to correct or address for joint-line movement associated withlost cartilage. Alternatively, the cartilage thickness can be measureddirectly in or more regions.

The sagittal and/or coronal curvatures of a patient's condyle can bedetermined from image data by assessing the surface of the condyle in asubstantially sagittal or coronal plane. Alternatively or in addition,the curvature(s) also can be assessed in an axial plane, for example fora patella, a trochlea, a glenoid, or an acetabulum. For example, asshown in FIG. 38, a patient's J-curve can be determined independentlyfor lateral and medial condyles. Then, one or both of the patient'slateral and medial condylar J-curves can be applied to one or moresections of a femoral implant component's medial and/or lateralJ-curves. For example, the distal point of the lateral condyle through arange of motion 3810 and the distal point of the medial condyle througha range of motion 3820 can independently be applied, respectively, to alateral sagittal plane 3830 defined by the patient's epicondylar axisand to a medial sagittal plane 3840 defined by the patient's epicondylaraxis to yield independent lateral and medial J-curves that are appliedto the patient-specific implant component. In certain embodiments, asshown in FIG. 38, a model of a patient's femur can be generated fromimages of the patient's femur. The images can include, for example,x-ray, cone beam CT, digital tomosynthesis, ultrasound, laser imaging,MRI, CT, PET, SPECT, and/or other images and combinations thereof. Incertain embodiments, as shown in FIG. 38, the patient's J-curve can betransferred onto a single plane (e.g., a substantially sagittal plane)and then that planar curvature, or a portion thereof, can be transferredinto the design of the femoral implant component as a single planarcurvature. In certain embodiments, the patient's J-curve can lie in morethan one plane and more than one plane can be used to transfer and applythe J-curve to the implant component, for example, such that the J-curvelies in one plane for a portion and then angles away from that plane fora portion. Moreover, in certain embodiments, one or both of the implantcomponent's condylar J-curves or portions thereof can match thepatient's J-curve planar orientation. For example, corresponding medialand lateral planes that include portions of the patient's medial andlateral J-curves, respectively, can be non-parallel to each other (e.g.,angled toward each other anteriorly) or otherwise angled relative to ananatomical feature (e.g., the epicondylar axis, femoral mechanical axis,trochlear J-curve, and/or some other feature). The corresponding J-curveportions of the femoral implant component and, optionally, the tibialimplant component can be designed to match this planar orientation. Forexample, the J-curve or portions thereof (e.g., the distal and/orposterior load-bearing portions) can match the patient's J-curve in asagittal direction or in both a sagittal and coronal direction.

In one embodiment, the medial or lateral femoral condyle can have aconstant coronal curvature, which can be standard or patient-derived orselected. The constant coronal curvature can be the same on the medialand the lateral condyle or it can be different. The constant coronalcurvature can be combined with a patient-specific or patient-derived, atleast in part, sagittal curvature on one or both condyles.

In a different embodiment, the same condyle can have two areas withdifferent constant coronal curvatures. For example, the central, distalload bearing portion of one or both femoral condyles can have adifferent constant coronal curvature than the high posterior portion ofone or both condyles. The use of two different constant coronalcurvatures in these different areas of the condyle can, for example, beadvantageous in select high-flexion designs whereby one or more constantcoronal curvatures are adapted or selected to maximize tibiofemoralcontact area and minimize tibiofemoral contact stress and resultant wearfor one or more flexion angles. More than two constant coronalcurvatures are possible on a condyle. The transition between a firstarea of constant coronal curvature and a second and, optionally, thirdor fourth, area of constant coronal curvature can be selected ordesigned to coincide with certain anatomic features, e.g. a sulcus line.The transition between a first area of constant coronal curvature and asecond and, optionally, third or fourth, area of constant coronalcurvature can be selected or designed to include one or two or multiplecoronal radii that allow for a smooth transition from a first to asecond area of constant coronal curvature.

In select high flexion designs, one or more of the posterior condylecurvature, implant thickness, edge thickness, bone cut orientation, andbone cut depth, can be adapted to maximize flexion. For example, theposterior bone cut can be offset more anteriorly for a given minimumthickness of the implant. This anterior offsetting of the posterior cutcan be combined with a taper of the posterior implant bearing surface.Other strategies to enhance a patient's deep knee flexion include addingor extending the implant component posteriorly, at the end bearingsurface in high flexion. By extending the bearing surface the knee canbe flexed more deeply. Accordingly, in certain embodiments, theposterior edge and/or posterior bearing surface is patient-engineered toenhance deep knee flexion for the particular patient.

Patellar revision can be very challenging and bone preservation ispreferred in the patella. In certain embodiments, two or more patellarresection facets and two or more patellar implant component bone cutsare employed to preserve patellar bone stock. One or both of the two ormore patellar facets can be substantially tangent or parallel to themedial and/or lateral uncut patellar surfaces. Optionally, particularlywith more than two patellar resection facets, facets can besubstantially tangent or parallel to uncut patellar superior and/orinferior surfaces. In certain embodiments, the patellar-facing surfaceof an implant component can be patient-specific, i.e., designed to matchthe patient's normal trochlear groove or patellar shape (e.g. patellarcartilage or subchondral bone). Alternatively, the patellar-facingsurface of the implant component can be engineered from patient-specificdata to optimize one or more parameters, for example, kinematics or wearbetween component surfaces. A method for designing a patient-adaptedimplant to optimize tracking of the patella along the trochlear grooveof a femoral implant component is described below in Example 8.Specifically, the exemplary implant design in Example 8 uses apatient-specific sagittal curvature, at least in part, and an engineeredcoronal curvature, at least in part, to allow the patella component totrack properly in the trochlear groove. In certain other embodiments,the coronal curvature additionally can be patient-specific. In certainembodiments, the coronal curvature is patient-specific and the sagittalcurvature is standard or engineered.

In certain embodiments, one or more trochlear groove features (e.g.,trochlear J-curve, sulcus displacement, and/or other features) andcorresponding patella features (articular surface contour and/orcurvature, ML, SI, and/or AP shape) can be patient-specific,patient-engineered, and/or standard, in part or in whole. For example,FIG. 39 shows the line of a trochlear J-curve defined anteriorly by thelowermost point of the patient's trochlear groove (i.e., sulcus) andsuperimposed on the patient's distal femur. As indicated by the figure,an implant's trochlear J-curve can substantially or partially match thepatient's trochlear J-curve (e.g., curve of sulcus viewed in thesagittal plane) in one or more locations, for example, in the anteriorportion of the trochlear J-curve. The substantially matching trochlearJ-curve can include portions that are smoothed relative to the patient'scurvature. The partially matching trochlear J-curve can include portionsthat are engineered or patient derived and smoothed or constant relativeto the patient's curvature. At the same time, the trochlear J-curveand/or sulcus position (e.g., shift in the trochlear J-curve in the MLdirection) of the implant can be engineered, in part or in whole, fromthe patient's anatomy, e.g., to improve kinematics. For example, asshown in FIG. 39, the distal portion of the trochlear J-curve is taperedout 1-2 mm, relative to the patient's trochlear J -curve. As discussedin detail below, the patellar implant component can include be selectedand/or designed to include one or more features that correspond to oneor more trochlear features of the femoral implant component.

In preferred embodiments, the implant's trochlear groove is slightlylarger (e.g., a curvature that is wider in the ML dimension and/orhaving a deeper sulcus) than the corresponding engaging surface of thepatella, and/or slightly larger than the patient's correspondingtrochlear groove. For example, in certain embodiments, the implantcomponent includes a trochlear groove coronal curvature that isengineered to be slightly wider and/or deeper than the patient'strochlear groove coronal curvature.

Moreover, the implant component can include a trochlear groove and/orsulcus that are shifted and/or angled in part or in whole, for example,in order to optimize the biomechanical situation during knee motion. Forexample, the implant component's trochlear groove and/or sulcus can beoffset by 2-5 mm medially, by 2-5 mm laterally, by about 2 mm medially,by about 2 mm laterally, by 1-2 mm medially, by 1-2 mm laterally, byless than 1 mm medially, or by less than 1 mm laterally, for example,relative to the patient's trochlear groove and/or sulcus and/or relativeto one or both of the medial and/or lateral condyles. For example, asshown in FIG. 40, in certain embodiments, a line 4010 intersecting thesulcus of the implant component and perpendicular to a baseline 4015connecting the lowermost points 4025, 4030 of the medial and lateralcondyles can be medial to the point 4040 on the baseline that bisectsthe lowermost points of the medial and lateral condyles. Alternativelyor in addition, the implant component's trochlear groove and/or sulcuscan be angled relative to the patient's trochlear groove and/or sulcus.For example, in certain embodiments the trochlear groove or sulcus ofthe implant component can be positioned to include the patient'sposterior aspect of the femoral trochlear notch or sulcus but then angleaway anteriorly (e.g., by less than 10 degree, such as by 5-7 degrees)from the patient's trochlear groove or sulcus either in the medialdirection or in the lateral direction.

In certain embodiments, the trochlear articulating surface of thefemoral implant component can include an overall shape thatsubstantially positively matches the shape of the patient's trochleararticulating surface, as shown in FIGS. 41A and 41B. In particular, FIG.41A depicts an axial view of a particular patient's femoral shape 4100,with the trochlear groove 4102, lateral anterior sulcus 4104, and medialanterior sulcus 4106 indicated by dashed lines. FIG. 41B depicts anoverlay of an implant component's articulating surface 4108 (dash-dotline) and the particular patient' femoral shape 4100 (solid line). Inthis figure, the shape of the implant component 4108 (from the axialview) is patient -specific such that it substantially positively matchesthe particular patient's femoral shape 4100 (from the axial view).Alternatively or in addition, one or more aspects of the implantcomponent's shape 4108 can be patient-engineered (e.g., derived frompatient-specific data and optimized relative to the shape of thepatient's femur 4100. For example, as shown in FIG. 41C, the implantcomponent's trochlear articulating surface includes an overhangingflange or extension 4110 at the intercondylar notch 4110. As shown inthe figure, the overhanging flange or extension 4110 extends from thelateral aspect of the intercondylar notch; however, in certainembodiments it can extend from the lateral or medial aspect, or both, ofthe intercondylar notch. This overhanging feature 4110 can be beneficialin patients with a wider intercondylar notch distance, in particular ifa standard patellar button (i.e., patellar implant component) is usedthat could, for example, be less wide than the intercondylar distance inselect patients. The extension or flange can assist to help avoidpatellar clicking or capture, for example, if a smaller patellar buttonmay “fall” into the intercondylar notch region during motion of theknee.

In certain embodiments, the implant component can substantially matchone or more of the patient's femoral or femoral condyle dimensions orsurface shapes (e.g., the shape of the patient's femoral bone orcartilage) on the joint-facing surface (e.g., at the bearing surfacethat engages the tibia) and, optionally, also on the bone-facingsurface. At the same time, the trochlear's outer, articulating shapecan, however, be partially matched to the patient's articular surfaceor, instead, patient-engineered from patient data but not designed tomatch the patient's surface feature. For example, as shown in FIG. 41D,the implant component can include a shallower trochlear groove 4114 thanthe patient's trochlear groove 4116. In the figure, the trochlear groovecurvatures 4114, 4116 are shown above the axial view of the femur 4100and implant component 4108. This shallower trochlear groove 4114 can beengineered by using a shallower lateral side of the trochlear surface4118 and/or a shallower medial side of the trochlea 4120, for examplerelative to the patient's lateral and medial sides. A shallower lateralshape of the implant component's trochlea surface 4118 can, for example,assist in achieving more normal patellofemoral motion in selectpatellofemoral tracking abnormalities. For example, as shown in FIG.41E, a shallower lateral shape of the implant component's trochleasurface 4118 can be used to correct a patient's tracking abnormalityrelating to the patient's lateral trochlear shape 4122. A shallowermedial shape of the implant component's trochlea surface 4120 can, forexample, assist in achieving more normal patellofemoral motion in selectpatellofemoral tracking abnormalities.

The partially (e.g., coronal plane only or lateral trochlear surfaceonly) or completely engineered (e.g., coronal plane and sagittal planeor medial and lateral trochlear surface) trochlear surface of theimplant component can be, at least in part, anterior to the patient'snative, uncut bone or it can be, at least in part, posterior to thepatient's native, uncut bone, or both. For example, as shown in FIG.41F, the implant component surface 4108 can be anterior to the patient'suncut medial trochlear bone surface 4124 but posterior to the patient'suncut lateral trochlear bone 4126. As shown in FIG. 41F, the implantcomponent surface 4108 can be anterior to the patient's uncut medialtrochlear bone surface 4122 but posterior to the patient's uncut lateraltrochlear bone 4124. The most posterior point of the partially orcompletely engineered trochlear articulating surface of the implant canbe anterior to, coincident with, or co-planar with, or posterior to themost posterior point of the patient's native, uncut trochlear in anylocation of the trochlea, e.g., superior, central, or inferior.

The coronal curvature also can be non-patient-matched or derived, orengineered or constant. Each of FIGS. 41G and 41H depict an exemplaryimplant component surface 4108 having a constant trochlear coronalcurvature that does not follow the patient's trochlear coronalcurvature. However, as shown by the figures, other implant componentfeatures (e.g., surface outline 4108) are patient-specific with respect(e.g., with respect to the patient's femoral surface outline 4100).

The trochlear articular surface can be patient-specific in alldimensions and aspects; patient-engineered in all dimensions or aspects;partially patient-specific and partially patient-engineered; partiallypatient-specific and partially standard; partially patient-engineeredand partially standard; or partially patient-specific, partiallypatient-engineered, and partially standard. Combinations include, forexample, those described in Table 9.

TABLE 9 Exemplary features of implant component trochlear surface Afirst implant component feature A second implant component featureCoronal J-curve patient-engineered Sagittal J-curve patient-specificSagittal J-curve patient-engineered Coronal J-curve patient-specificMedial trochlear surface patient- Lateral trochlear surface engineeredpatient-specific Lateral trochlear surface patient- Medial trochlearsurface engineered patient-specific Superiorly patient-engineeredInferiorly patient-specific Inferiorly patient-engineered Superiorlypatient-specific

Of note, an engineered surface can still include patient-derivedparameters. For example, the patient's trochlear coronal curvature canbe measured in multiple locations and an average can be derived. Theaverage or constant coronal curvature can then be applied to thearticulating surface of the implant. Optionally, a matching patellarimplant component can be selected or designed.

The trochlear groove location can be patient derived, e.g., derived fromthe location of the patient's uncut trochlear groove determined from animaging test. A desired trochlear groove location can be derived basedon these measurements, for example by calculating a straight lineintersecting the patient's curved trochlear groove. Mathematical orkinematic modeling can be used to derive the patient-derived, engineeredtrochlear groove location.

The sagittal curvature of the articulating trochlear surface of thefemoral component can be matched to the patient's sagittal trochlearshape in one or more locations, e.g., trochlear groove, medial trochleaor lateral trochlea or combinations thereof;

-   -   matched to the patient's sagittal trochlear shape superiorly,        but engineered inferiorly, e.g., in the trochlear groove, medial        trochlea or lateral trochlea or combinations thereof;    -   matched to the patient's sagittal trochlear shape inferiorly,        but engineered superiorly, e.g., in the trochlear groove, medial        trochlea or lateral trochlea or combinations thereof; and/or    -   anterior or posterior or combinations thereof to the patient's        uncut trochlea in different sections of the patient's trochlea.

The trochlear groove curvature and/or location can be patient-specificon the implant articulating surface, i.e., replicating the location ofthe patient's native, uncut trochlear groove, for example as it extendsfrom superior to inferior. For example, FIG. 41I depicts an implantcomponent trochlear groove 4126 that is patient-specific tosubstantially match the patient's trochlear groove curvature 4128 andposition. The trochlear groove location can be patient-engineered, e.g.,to include one or more straight, curved, straight oblique, and/or curvedoblique sections that may deviate from the patient's trochlear groove.The trochlear groove can be a combination of patient-specific andpatient-engineered. For example, FIG. 41K depicts an implant componenttrochlear groove 4126 that is patient-specific in its shape tosubstantially positively match the shape of the patient's trochleargroove curvature 4128; however, the implant component trochlear groove4126 is offset laterally in its location relative to the patient'strochlear groove curvature 4128. Moreover, FIGS. 41K and 41L (FIG. 41Lis a blown-up image of the trochlear groove depicted in FIG. 41K) depictan implant component trochlear groove 4126 that is a patient-derived tobe patient-specific in part and patient-engineered in part to yield astraight trochlear groove 4126. In particular, the location andcurvature of the patient's trochlear groove is measured and then, in theimplant component, the trochlear groove is patient-specific where thepatient's groove is straight and patient-engineered where the patient'sgroove curves. Alternatively a patient -engineered straight trochleargroove can be derived as an average straight line based on the patient'sgroove. Alternative, the patient-engineered line can be forced to followan oblique line rather than a straight line.

Alternatively, the implant component trochlear groove 4126 can be astandard straight line 4130 or oblique line 4132, as shown in FIGS. 41Mand 41N, respectively.

FIG. 41O depicts a patient anatomy sagittal cross-section through thetrochlear groove and FIG. 41P through 41V depict the same patientanatomy sagittal cross-section (solid line) overlaid with an implantcomponent sagittal cross-section through the trochlear groove. Inparticular, FIG. 41P depicts an implant component having a sagittalshape that is patient-specific to match the patient's sagittal shape.FIGS. 41Q and 41T depict implant components having a sagittal shape thatis patient-specific with respect to the inferior trochlea shape andpatient-engineered with respect to the superior trochlea shape. FIGS.41R and 41S depict implant components having a sagittal shape that ispatient-specific with respect to the superior trochlea shape andpatient-engineered with respect to the inferior trochlea shape.

FIGS. 41U and 41V depict implant components that are patient-specificand have a completely engineered sagittal trochlear curvature.

As noted above, with traditional knee implants the patient's bone isresected to fit the standard shape of the bone-facing surface of thetraditional femoral implant component. On its bone-facing surface, thetraditional femoral implant component includes five standard bone cuts,as exemplified by the implant shown in FIG. 42A. Specifically, atraditional total knee implant includes a distal or horizontal cut 4210,an anterior cut 4220, a posterior cut 4230 along each femoral condyle,an anterior chamfer cut 4240, and a posterior chamfer cut 4250.

In certain embodiments, one or more portions of the bone-facing surfaceof the femoral implant are designed based on patient-specific data tosubstantially negatively-match the uncut surface of the patient's femur,for example, the subchondral bone surface of the femur. In suchembodiments, the surgical procedure includes resurfacing (i.e., removingcartilage, at least in part, while substantially retaining the surfaceof subchondral bone (i.e. cutting away bone), the joint-facing surfaceof the patient's femur. In certain embodiments, the bone-facingsurface(s) of the implant component are designed and/or selectedpreoperatively, based on patient-specific data, to optimize one or moreparameters, such as bone preservation (e.g., minimizing the amount ofbone that is resected during the implant procedure).

In certain embodiments one or more portions of the bone-facing surfaceof the femoral implant includes two or more bone cuts, for example, two,three, four, five, six, seven, eight, nine, or more bone cuts. Forexample, a femoral implant component can include less than or greaterthan five bone cuts. In a preferred embodiment, the femoral implantincludes six bone cuts, as shown in FIG. 42B. In another preferredembodiment, the femoral implant includes seven bone cuts, as shown inFIG. 6B. One or more of the implant bone cuts can be curvilinear or theentire bone-facing surface of the implant component can be curvilinearbone cut.

As exemplified in FIG. 42C, in certain embodiments the femoral implantand design can include bone cuts that are rotated or oriented based on acertain flexion angle of the knee, e.g., rotated in the sagittal plane.An example of a flexed-fit cut design is described in Example 2, below.Any number of bone cuts can be included in an implant device designedwith flexed-fit cuts. For example, two, three, four, five, six, seven,eight, nine or more cut planes can be included in a flexed-fit design.One or more of the cuts can be curvilinear or the entire bone-facingsurface can be curvilinear. Moreover, any one or more bone cuts caninclude two or more non-coplanar facets, as described below. The cutscan be oriented at any rotation, for example, at 5, greater than 5, 10,greater than 10, 15, greater than 15, 20, greater than 20, 25, orgreater than 25 degrees flexion.

In certain embodiments, the femoral implant component can include one ormore bone cuts oriented one or more dimensions, e.g., not only in thesagittal plane, but also in the coronal plane and/or in the axial plane.FIGS. 43A through 43F show exemplary cross -sections of femoral implantcomponents with bone cuts shown as dashed lines. FIGS. 43A and 43B showan implant component with traditional bone cuts (FIG. 43A) as comparedto an implant component with bone cuts rotated in the sagittal plane(FIG. 43B). FIGS. 43C and 43D show an implant component with traditionalbone cuts (FIG. 43C) as compared to an implant component with bone cutsrotated in the coronal plane (FIG. 43D). FIGS. 43E and 43F show animplant component with traditional bone cuts (FIG. 43E) as compared toan implant component with bone cuts rotated in the axial plane (FIG.43F). Such bone cut rotations can help to further optimize bonepreservation.

As shown in FIGS. 44A-44C and 45A-45B, in certain embodiments an implantcomponent bone cut can include one or more non-parallel and non-coplanarfacets. As shown, the implant component in FIG. 44A includes six bonecuts while the implant component in FIG. 45A includes an extra posteriorchamfer bone cut for a total of seven bone cuts. Non-coplanar facets caninclude facets that lie in parallel but different planes and/or facetsthat lie in non-parallel planes. As exemplified by the implant componentshown in FIGS. 44A-44B and by the implant component shown in FIGS.45A-45B, the medial and lateral facets of a bone cut can be non-paralleland non-coplanar for one or more bone cuts, for example, for one or moreof the distal bone cut 4410, the posterior bone cut 4430, the firstposterior chamfer bone cut 4452, and the second posterior chamfer bonecut 4454. Alternatively or in addition, one or more corresponding facetsof a bone cut can include different thicknesses. For example, theimplant component shown in FIG. 44A includes a maximum distal medialfacet thickness of 6.2 mm and a maximum distal lateral facet thicknessof 6.3 mm. The independent and optionally patient-derived thicknesses oncorresponding bone cut facets can apply to one or more thicknessmeasurements, for example, one or more of maximum thicknesses, minimumthickness, and an average thickness, for example, to match or optimizethe particular patient's anatomy. Moreover, a single bone cut or bonecut facet can include a variable thickness (e.g., a variable thicknessprofile across its M-L and/or A-P dimensions. For example, a bone cut orbone cut facet can include a thickness profile in one or more dimensionsthat is patient-derived (e.g., to match or optimize the patient'sanatomy). The implant component in FIG. 45A includes an anterior chamferwith an 11 mm thickness on the medial side (which includes the medialimplant component peg or post 4465) and a different thickness on thelateral side. As shown, the implant component in FIG. 45A was selectedand/or designed to have a flex-fit (e.g., having bone cuts rotatedposteriorly about the transepicondylar axis, which can enhance implantcomponent coverage of the posterior portion of the femur and provide thepatient with deeper knee flexion with the implant.

Alternatively or in addition, one or more corresponding facets of a bonecut can include different surface areas or volumes. For bone cuts havingfacets separated by the intercondylar space and asymmetric with respectto the A-P plane bisecting the implant component, the asymmetric facetsappear dissimilar in shape and/or size (e.g., two-dimensional area). Forexample, the implant components shown in FIGS. 44A and 45A include oneor more corresponding facets (e.g., distal medial and lateral facets,posterior medial and lateral facets, and/or posterior chamfer medial andlateral facets) having different medial facet and lateral facetbone-facing surface areas, joint-facing surface areas, and/or volumes inbetween the two surfaces. In particular, as shown in FIGS. 44A and in45A, the medial and lateral facets of the distal bone cut 4410 areasymmetric and appear dissimilar in both shape (e.g., surface areaperimeter shape) and size (e.g., volume under the surface area). Theindependent facet surface areas and/or volumes optionally can bepatient-derived (e.g., to match or optimize the patient's anatomy).

As shown in FIG. 44A, non-coplanar facets can be separated by anintercondylar space 4414 and/or by a step cut 4415. For example, asshown in the figure, the distal bone cut 4410 includes non-coplanarmedial and lateral facets that are separated, in part, by theintercondylar space 4414 and, in part, by a step cut 4415.

In certain embodiments, one or more resection cuts can be selectedand/or designed to so that one or more resected cut or facet surfacessubstantially matches one or more corresponding bone cuts or bone cutfacets. For example, FIG. 44C shows six resection cut facets thatsubstantially match the corresponding implant component bone cut facetsshown in FIG. 44A. FIG. 45B shows seven resection cut facets thatsubstantially match the corresponding implant component bone cut facetsof the medial side of the implant component shown in FIG. 44A. Theportion 4470 represents additional bone conserved on the lateral side ofthe of the femur corresponding to the bone-cut intersection between thelateral distal bone cut facet 4410 and the adjacent anterior chamferbone cut 4440.

In certain embodiments, a bone-cut facet and/or a resection cut facetcan span the intercondylar space and be separated from another facet bya step cut. For example, as exemplified in FIG. 46, predeterminedresection cuts can be selected and/or designed to include a facet orpart of a facet 4680 separated from one or more corresponding facets byan intercondylar space 4614 and/or by a step cut 4615.

In addition or alternatively, in certain embodiments one or more of theimplant bone cuts can be asymmetric, for example, asymmetric withrespect to a sagittal or A-P plane, or to a coronal or M-L plane,bisecting the implant component. For example, as shown in FIGS. 44A and45A, the anterior chamfer bone cut 4440 is asymmetric with respect to anA-P plane bisecting the implant component. In addition, in both figuresthe lateral distal bone cut facet 4410 is asymmetric with respect to anA-P plane bisecting the implant component.

The bone cut designs described above, for example, an implant componentbone-facing surface having various numbers of bone cuts, flexed bonecuts, non-coplanar bone cut facets, step cuts used to separate facets,and asymmetric bone cuts and bone cut facets, can be employed on abone-facing surface of a femoral implant component to save substantialportions of bone. Table 10 shows the different amounts of bone to beresected from a patient for fitting an implant component with bone cutsshown in FIG. 44A, an implant component with bone cuts shown in FIG.44A, and a traditional implant component with traditional bone cuts. Ascompared to the traditional implant component, the implant componentshown in FIG. 44A saves 44% of resected patient bone and the implantcomponent shown in FIG. 45A saves 38% of resected patient bone. However,the implant component in FIG. 45A is flexed, which can provide enhanceddeep knee flexion for the patient. In certain embodiments, the surgeonor operator can select or apply a weighting to these two parameters(bone preservation and kinematics) and optionally other parameters toidentify an optimum patient-adapted implant component and, optionally, acorresponding resection cut strategy, that meets the desired parametersand/or parameter weightings for the particular patient.

TABLE 10 Bone preservation comparison using different bone cut designsFIG. 9E FIG. 9D Implant Implant (Flexed Traditional Bone Cut (Stepped)no step) Implant Distal Medial 3626 2675 5237 Distal Lateral 2593 30772042 Medial Posterior Chamfer 1 942 694 3232 Lateral Posterior Chamfer 1986 715 648 Medial Posterior Chamfer 2 816 921 — Lateral PosteriorChamfer 2 612 582 — Medial Posterior Cut 945 1150 2816 Lateral PosteriorCut 770 966 649 Anterior Chamfer 1 1667 6081 9872 Anterior Chamfer 2 —1845 — Anterior Cut 3599 2717 4937 Total bone resection (mm³)* 1655618346 29433 Reduction in bone resected as 44% 38% — compared totraditional implant

In traditional femoral implant components, the anterior or trochlearbone cut is located substantially in the coronal plane and is parallelto the posterior condylar bone cut, as indicated by the dashed anteriorresection cut 4710 and dashed posterior resection cut 4712 shown in FIG.47A. This can result in a substantial amount of bone lost from thoseportions of the patient's femur 4714, 4716. However, in certainembodiments described herein, the implant's anterior or trochlear bonecut is substantially non-parallel to the coronal plane, as shown by thedashed and straight line 4718 in FIG. 47B. For example, the implant'santerior or trochlear bone cut can substantially match the patient'sresected trochlear surface, which can be selected and/or designed to beparallel to a tangent through the corresponding peak 4720 and an uncuttrochlear surface portion of the patient's trochlea, as shown in FIG.47B. By placing the implant bone cut 4718 and the resected surface at anangle relative to the patient's coronal plane, for example, parallel toa tangent of one or both medial and lateral trochlear peak and/or theadjacent trochlear surface, a substantial amount of bone can bepreserved.

In certain embodiments, the implant component can include a trochlearbone cut with two or more non-coplanar facets, as shown by theintersecting solid lines 4722, 4724 in FIG. 47B. For example, one of thetwo or more facets (and the patient's corresponding resected surface)can be substantially parallel to the patient's lateral uncut trochlearpeak 4720 and/or the adjacent uncut trochlear surface. A second facet(and the patient's corresponding resected surface) can be substantiallyparallel to the patient's medial uncut trochlear peak 4726 and/or theadjacent uncut trochlear surface. This can further enhance the degree ofbone preservation.

In certain embodiments, two or more trochlear bone cut facets can besubstantially tangent to the lateral and medial patellar surfaces 4728,4730 of the patient's uncut bone. In addition or alternatively, two ormore trochlear bone cuts can be substantially tangent or parallel to thesuperior and inferior patellar facets, in particular, when more than twoimplant trochlear bone cut facets are used. In certain embodiments, oneor more trochlear bone cut facets can be curvilinear.

In a traditional femoral implant component, the posterior bone cutincludes portions on the medial and lateral condyles that are in thesame plane and parallel to each other, and substantially parallel to theanterior cut. However, in certain embodiments described herein, theimplant component can include posterior condylar bone cut facets on themedial and lateral condyles, respectively, that are non-coplanar 4732,4734. Alternatively, or additionally, the implant component can includeone or more posterior condylar facets that are substantiallynon-parallel with one or more facts of the anterior bone cut.

In certain preferred embodiments, the posterior condylar bone cutincludes a facet on the medial condyle that is substantiallyperpendicular to the long axis of the medial condyle. Optionally, thefacet on the lateral condyle can be perpendicular to the long axis ofthe lateral condyle. As depicted in FIG. 48, in certain embodiments, theanterior bone cut and corresponding resection cut 4810 and posteriorbone cut 4820 can be substantially non-parallel to the coronal plane4830 in the superoinferior orientation.

In certain embodiments, the posterior bone cut medial and lateral facetsof an implant component can be asymmetric with respect to an A-P planebisecting the implant component. Moreover, one or more posterior bonecut facets can be curvilinear.

In certain embodiments, the distal bone cut of a femoral implantcomponent includes medial and lateral condylar facets that are in thesame plane as each other and/or are substantially parallel to eachother. The facets can be separated by the intercondylar space and/or bya step cut. In certain embodiments, the implant component can include adistal bone cut having medial and lateral condylar facets that arenon-coplanar and/or non-parallel.

In certain embodiments, the distal bone cut or bone cut facets is/areasymmetric with respect to an A-P plane bisecting the implant component.Moreover, the distal bone cut and/or one or more distal bone cut facetscan be curvilinear.

Traditional femoral implant components include one anterior chamfer bonecut and one posterior chamfer bone cut. However, in certain embodimentsdescribed herein, additional chamfer bone cuts can be included. Byincreasing the number of chamfer bone cuts on the implant and placingthe cuts in close proximity to the tangent of the articular surface,additional bone can be preserved. One or more additional chamfer bonecuts can be substantially tangent to the articular surface. For example,in certain embodiments, the implant component can include one or moreadditional anterior chamfer cuts and/or one or more additional posteriorchamfer cuts.

In certain embodiments, the implant component can include a posteriorchamfer bone cut that includes medial and lateral condylar facets thatare non-coplanar and/or non-parallel. In certain embodiments, aposterior chamfer bone cut of the implant component can include facetsthat are asymmetric with respect to an A-P plane bisecting the implantcomponent. Moreover, one or more posterior chamfer bone cuts and/or oneor more posterior chamfer bone cut facets can be curvilinear.

In certain embodiments, the implant component can include an anteriorchamfer bone cut that includes medial and lateral condylar facets thatare non-coplanar and/or non-parallel. In certain embodiments, ananterior chamfer bone cut of the implant component can be asymmetricand/or can include facets that are asymmetric with respect to ananterior -posterior (A-P) plane bisecting the implant component.Moreover, one or more anterior chamfer bone cuts and/or bone cut facetscan be curvilinear.

In certain embodiments, the cut plane for one or more bone cuts of theimplant component, for example, the distal bone cut and/or one or moreof the anterior chamfer bone cuts, can be defined, in part, by theextent of the trochlear gap in the patient's joint. Specifically, one ormore of these bone cuts can be designed based on patient-specific datato include a perimeter that matches the contour of the patient'strochlear notch. In certain embodiments, the implant component ispatient-adapted so that there is no exposed implant surface on thebone-facing side of the implant component at the trochlear gap.Moreover, one or more of these bone cuts can be designed so that thereis no, or minimally exposed, resected bone surface at the trochlearnotch.

Computer software can be used that calculates the closest locationpossible for resected surfaces and resected cuts relative to thearticular surface of the uncut bone, e.g., so that all intersects ofadjoining resected surfaces are just within the bone, rather thanoutside the articular surface. The software can move the cutsprogressively closer to the articular surface. When all intersects ofthe resected cuts reach the endosteal bone level, the subchondral bonelevel, and/or an established threshold implant thickness, the maximumexterior placement of the resected surfaces is achieved and, with that,the maximum amount of bone preservation.

In addition to the implant component features described above, certainembodiments can include features and designs for cruciate substitution.These features and designs can include, for example, an intercondylarhousing (sometimes referred to as a “box”) 4910, as shown in FIGS. 49Aand 49B, and/or one or more intercondylar bars 5010, as shown in FIGS.50A and 50B, as a receptacle for a tibial post or projection. Theintercondylar housing, receptacle, and/or bars can be used inconjunction with a projection or post on a tibial component as asubstitute for a patient's posterior cruciate ligament (“PCL”), whichmay be sacrificed during the implant procedure. Specifically, as shownin FIGS. 50A and 50B, the intercondylar housing, receptacle or barsengage the projection or post on the tibial component to stabilize thejoint during flexion, particular during high flexion.

In certain embodiments, the femoral implant component can be designedand manufactured to include the housing, receptacle, and/or bars as apermanently integrated feature of the implant component. However, incertain embodiments, the housing, receptacle, and/or bars can bemodular. For example, the housing, receptacle, and/or bars can bedesigned and/or manufactured separate from the femoral implant componentand optionally joined with the component, either prior to (e.g.,preoperatively) or during the implant procedure. Methods for joining themodular intercondylar housing to an implant component are described inthe art, for example, in U.S. Pat. No. 4,950,298. As shown in FIG. 51,modular bars 5110 and/or a modular box 5120 can be joined to an implantcomponent at the option of the surgeon or practitioner, for example,using spring-loaded pins 5130 at one or both ends of the modular bars.The spring-loaded pins can slideably engage corresponding holes ordepressions in the femoral implant component.

The portion of the femoral component that will accommodate the housing,receptacle or bar can be standard, i.e., not-patient matched. In thismanner, a stock of housings, receptacles or bars can be available in theoperating room and added in case the surgeon sacrifices the PCL. In thatcase, the tibial insert can be exchanged for a tibial insert with a postmating with the housing, receptacle or bar for a posterior stabilizeddesign.

The intercondylar housing, receptacle, and/or one or more intercondylarbars can include features that are patient-adapted (e.g.,patient-specific or patient-engineered). In certain embodiments, theintercondylar housing, receptacle, and/or one or more intercondylar barsincludes one or more features that are designed and/or selectedpreoperatively, based on patient-specific data including imaging data,to substantially match one or more of the patient's biological features.For example, the intercondylar distance of the housing or bar can bedesigned and/or selected to be patient-specific. Alternatively or inaddition, one or more features of the intercondylar housing and/or oneor more intercondylar bars can be engineered based on patient-specificdata to provide to the patient an optimized fit with respect to one ormore parameters. For example, the material thickness of the housing orbar can be designed and/or selected to be patient-engineered. One ormore thicknesses of the housing, receptacle, or bar can be matched topatient-specific measurements. One or more thicknesses of the housing,receptacle, and/or bar can be adapted based on one or more implantdimensions, which can be patient-specific, patient-engineered orstandard. One or more thicknesses of the housing, receptacle or bar canbe adapted based on one or more of patient weight, height, sex and bodymass index. In addition, one or more features of the housing and/or barscan be standard.

Different dimensions of the housing, receptacle or bar can be shaped,adapted, or selected based on different patient dimensions and implantdimensions. Examples of different technical implementations are providedin Table 11. These examples are in no way meant to be limiting. Someoneskilled in the art will recognize other means of shaping, adapting orselecting a housing, receptacle or bar based on the patient's geometryincluding imaging data.

TABLE 11 Examples of different technical implementations of acruciate-sacrificing femoral implant component Box, receptacle or bar orspace defined by bar and Patient anatomy, e.g., derived from imagingstudies or condylar implant walls intraoperative measurementsMediolateral width Maximum mediolateral width of patient intercondylarnotch or fraction thereof Mediolateral width Average mediolateral widthof intercondylar notch Mediolateral width Median mediolateral width ofintercondylar notch Mediolateral width Mediolateral width ofintercondylar notch in select regions, e.g. most inferior zone, mostposterior zone, superior one third zone, mid zone, etc. Superoinferiorheight Maximum superoinferior height of patient intercondylar notch orfraction thereof Superoinferior height Average superoinferior height ofintercondylar notch Superoinferior height Median superoinferior heightof intercondylar notch Superoinferior height Superoinferior height ofintercondylar notch in select regions, e.g. most medial zone, mostlateral zone, central zone, etc. Anteroposterior length Maximumanteroposterior length of patient intercondylar notch or fractionthereof Anteroposterior length Average anteroposterior length ofintercondylar notch Anteroposterior length Median anteroposterior lengthof intercondylar notch Anteroposterior length Anteroposterior length ofintercondylar notch in select regions, e.g. most anterior zone, mostposterior zone, central zone, anterior one third zone, posterior onethird zone etc.

The height or M-L width or A-P length of the intercondylar notch can notonly influence the length but also the position or orientation of a baror the condylar walls.

The dimensions of the housing, receptacle or bar can be shaped, adapted,or selected not only based on different patient dimensions and implantdimensions, but also based on the intended implantation technique, forexample intended femoral component flexion or rotation. For example, atleast one of an anteroposterior length or superoinferior height can beadjusted if an implant is intended to be implanted in 7 degrees flexionas compared to 0 degrees flexion, reflecting the relative change inpatient or trochlear or intercondylar notch or femoral geometry when thefemoral component is implanted in flexion.

In another example, the mediolateral width can be adjusted if an implantis intended to be implanted in internal or external rotation,reflecting, for example, an effective elongation of the intercondylardimensions when a rotated implantation approach is chosen. The housing,receptacle, or bar can include oblique or curved surfaces, typicallyreflecting an obliquity or curvature of the patient's anatomy. Forexample, the superior portion of the housing, receptacle, or bar can becurved reflecting the curvature of the intercondylar roof. In anotherexample, at least one side wall of the housing or receptacle can beoblique reflecting an obliquity of one or more condylar walls.

The internal shape of the housing, receptacle or bar can include one ormore planar surfaces that are substantially parallel or perpendicular toone or more anatomical or biomechanical axes or planes. The internalshape of the housing, receptacle, or bar can include one or more planarsurfaces that are oblique in one or two or three dimensions. Theinternal shape of the housing, receptacle, or bar can include one ormore curved surfaces that are curved in one or two or three dimensions.The obliquity or curvature can be adapted based on at least one of apatient dimension, e.g., a femoral notch dimension or shape or otherfemoral shape including condyle shape, or a tibial projection or postdimension. The internal surface can be determined based on generic orpatient-derived or patient-desired or implant -desired kinematics inone, two, three or more dimensions. The internal surface can mate with asubstantially straight tibial projection or post, e.g., in the ML plane.Alternatively, the tibial post or projection can have a curvature orobliquity in one, two or three dimensions, which can optionally be, atleast in part, reflected in the internal shape of the box. One or moretibial projection or post dimensions can be matched to, designed to,adapted to, or selected based on one or more patient dimensions ormeasurements. Any combination of planar and curved surfaces is possible.

In certain embodiments, the position and/or dimensions of the tibialplateau projection or post can be adapted based on patient-specificdimensions. For example, the post can be matched with the position ofthe posterior cruciate ligament or the PCL insertion. It can be placedat a predefined distance from anterior or posterior cruciate ligament orligament insertion, from the medial or lateral tibial spines or otherbony or cartilaginous landmarks or sites. By matching the position ofthe post with the patient's anatomy, it is possible to achieve a betterfunctional result, better replicating the patient's original anatomy.

Similarly, the position of the box or receptacle or bar on the femoralcomponent can be designed, adapted, or selected to be close to the PCLorigin or insertion or at a predetermined distance to the PCL or ACLorigin or insertion or other bony or anatomical landmark. Theorientation of the box or receptacle or bar can be designed or adaptedor selected based on the patient's anatomy, e.g. notch width or ACL orPCL location or ACL or PCL origin or insertion.

FIGS. 52A through 52K show various embodiments and aspects ofcruciate-sacrificing femoral implant components. FIG. 52A shows a boxheight adapted to superoinferior height of intercondylar notch. Thedotted outlines indicate portions of the bearing surface and posteriorcondylar surface as well as the distal cut of the implant. FIG. 52Bshows a design in which a higher intercondylar notch space is filledwith a higher box or receptacle, for example, for a wide intercondylarnotch. FIG. 52C shows a design in which a wide intercondylar notch isfilled with a wide box or receptacle. The mediolateral width of the boxis designed, adapted or selected to the wide intercondylar notch. FIG.52D shows an example of an implant component having a box designed for anarrow intercondylar notch. The mediolateral width of the box isdesigned, adapted or selected for the narrow intercondylar notch. FIG.52E shows an example of an implant component having a box for a normalsize intercondylar notch. The box or receptacle is designed, adapted orselected for its dimensions. (Notch outline: dashed and stippled line;implant outline:dashed lines). FIG. 52F shows an example of an implantcomponent for a long intercondylar notch. The box or receptacle isdesigned, adapted or selected for its dimensions (only box, not entireimplant shown). FIG. 52G is an example of one or more oblique walls thatthe box or receptacle can have in order to improve the fit to theintercondylar notch. FIG. 52H is an example of a combination of curvedand oblique walls that the box or receptacle can have in order toimprove the fit to the intercondylar notch. FIG. 52I is an example of acurved box design in the A-P direction in order to improve the fit tothe intercondylar notch. FIG. 52J is an example of a curved design inthe M-L direction that the box or receptacle can have in order toimprove the fit to the intercondylar notch. Curved designs are possiblein any desired direction and in combination with any planar or obliqueplanar surfaces. FIG. 52K is an example of oblique and curved surfacesin order to improve the fit to the intercondylar notch. FIGS. 52Lthrough 52P show lateral views of different internal surfaces of boxes.

Femoral implant components of certain embodiments also can include otherfeatures that are patient-specific and/or optimized according to one ormore of the parameters discussed above.

A variety of peg configurations can be used for the implant componentsdescribed herein (femoral implant components as well as other implantcomponents). Exemplary configurations are illustrated in FIG. 53A. Incertain embodiments, the peg cross -section can be round. In certainembodiments, as illustrated in FIG. 53B, the peg cross-section caninclude a “+” or cross-like configuration, which may aid inmanufacturing. For example, in layering processes (used to create acasting blank), such as stereolithography (SLA), selective lasersintering (SLS), or fused deposition modeling (FDM), (generating orbuilding) the curved edges of a blank typically is more difficult thanthat of the straight-edges of a blank. Accordingly, the straight-edgesof the “+” configured peg may allow for a simpler (and better defined)blank used in the casting process as compared to a round peg.

A variety of peg sizes can be used for a bicompartmental implant orimplant component. For example, a 5 mm peg, a 6 mm peg, a 7 mm peg, oranother peg size can be used. The peg can reflect a variety ofconfigurations, for example, a “+” configured peg, can be used. The pegcan be oriented on the device at any angle. For example, one or morepegs can be oriented in line with the femoral mechanical axis.Alternatively, one or more pegs can be oriented at an anterior-leaningangle as the peg extends from the implant. For example, one or more pegscan be oriented anteriorly 5 degrees, 5-10 degrees, 10 degrees, 10-15degrees, and/or 15 degrees in an anterior-leaning angle relative to thefemoral mechanism axis. The pegs can be oriented at the same angle or atdifferent angles as one or both of the anterior and posterior cuts ofthe implant component. Pegs on a single implant component can havedifferent diameters, lengths or other features in accordance withindependently designed portions of the implant component.

The design of a bone cement pocket or pockets of an implant componentalso may include features that are patient-specific and/or optimizedaccording to one or more of the parameters discussed above. FIGS. 54Aand 54B show bone cement pockets in a component of certain embodiments(FIG. 54A) and in a traditional component (FIG. 54B). As shown in FIG.54A, each section or facet of the bone-facing surface of the componentcan have an independent cement pocket. One or more of the cement pocketscan be offset from the periphery by 2 mm or more. Each pocket can have amaximum depth of less than 0.9 mm, for example, 0.5 mm or less.

A preferred embodiment of the femoral implant component and resectioncuts is illustrated in FIGS. 55A through 55F. As shown FIGS. 55A and55B, the distal resection cuts are symmetric 5510 with less boneresected from the lateral posterior resection cut 5520. These featuresare matched on the inner, bone-facing surface of the implant. As shownin FIG. 55C, the anterior surface of the implant component includes aunique superior edge 5530. As shown, the superior edge includes lateraland medial superior curvatures with a trough in between. The lateralsuperior curvature is higher (e.g., more superior to) the medialsuperior curvature, and is about 2× higher relative to the lowest pointin the trough between them. As shown in FIG. 55D, the trochlear peaks5540 of the implant are lower than the patient's natural trochlear peaksand an 18 mm intercondylar distance 5550 is used with the implantcomponent. To achieve this intercondylar distance, the lateral condyleof the implant is slightly medialized 5555 relative to the patient'slateral condyle, and intercondylar notch coverage 5560 is increasedrelative to the patient's intercondylar notch. FIGS. 55E and 55Fillustrate the implant component from the opposite direction to show thenotch roof with slightly overhanging coverage 5565 on the lateralintercondylar (FIG. 55E) and the slightly medialized lateral condyle5555 resulting in exposed bone-facing surface on the medial side of theimplant's lateral condyle (FIG. 55F).

6.2 Patella Implant Component

In a traditional patellar implant procedure, the articular surface(i.e., the bearing surface and/or joint-facing surface) of a patient'spatella can be resected, typically using a bone cut across the patella,and a patellar implant component having standard dimensions can bemounted to the resected surface of the remaining portion of thepatient's patella. The patella implant components have off-the-shelfstandard dimensions and are typically selected intraoperatively.

In certain embodiments, an imaging test such as x-ray imaging, digitaltomosynthesis, cone beam CT, a CT scan including a spiral CT scan, MRIscan including 3D acquisitions, ultrasound scan, laser scan, opticalcoherence tomography or combinations thereof can be used to define theshape or geometry of a patient's patella and, optionally one or moreother biological or kinematic features. The scan data can be utilized tomeasure or derive information on the shape or geometry of the patient'spatella. For example, a superoinferior or mediolateral or obliquedimension or an anteroposterior width can be measured. One or morepatellar axes can be determined, e.g., a sagittal axis, coronal axis,axial axis, a tracking axis, one or more axes describing patellar motionin relationship to the trochlea, e.g., mediolateral or superoinferior oroblique, as well as select femoral axes, e.g., a posterior condylaraxis, epicondylar axis, Whiteside's line, a mechanical axis and/or onemore other axes. Someone skilled in the art will recognize otherpatellar- and axis-related measurements that can be obtained. Inprincipal, any anatomic or functional measurement applicable to apatellar geometry or function and kinematics can be obtained or derived.Once one or more geometric, functional, and kinematic measurements havebeen obtained or derived, the information can be utilized to select ordesign a patellar implant or component that is best suited for aparticular patient.

For example, an AP dimension of the patella can be measured and apatellar implant or component best matching the AP dimension can beselected and/or designed. The selection or design can be adapted basedon an intended resection depth. An ML dimension of a patellar implant orcomponent can be measured and a patellar implant or component bestmatching the ML dimension can be selected or designed. The selection ordesign can be adapted based on an intended resection depth. The APmeasurement or ML measurement or any other measurement can be adapted orderived for a preferred resection depth or cut depth. Resection forplacing the patellar implant or component can be achieved with anytechnique known in the art, such as sawing, burring, drilling, and/orother known techniques.

FIGS. 56A to 56C demonstrate how a patellar resection depth alters theresultant patellar resection profile (e.g., the profile of the cutsurface on the remaining patella). In general, as the resection planemoves away from the patellar articulating surface cartilage orsubchondral bone and deeper into the patella, a greater resultant APand/or ML resection dimension is produced until about the half point hasbeen crossed; at which point, typically, the resection profile starts todecrease in thickness resulting in a decrease in the AP and/or MLdimension of the resected profile. Thus, as shown in FIGS. 56A and 56B,a patellar implant or component can include a perimeter selected and/ordesigned for a particular resection depth. The resection can be plannedon a 2D image or a series of 2D images, or a 3D image or representation.The implant can be selected and/or designed on the 2D image or series of2D images, or 3D image or representation, for example by superimposing a2D or 3D outline of the implant. Multiple outlines can be available.Alternatively, as shown in FIG. 56C, a 2D or 3D outline can be smoothedor deformed to achieve the best or desired fit.

For example, in certain embodiments, the patellar implant or implantcomponent can be selected and/or designed so that it is substantiallymatches one or more AP or ML or oblique or other dimensions in at leasta portion of the uncut patella and/or in at least a portion of thepatella resection profile. Alternatively or in addition, the patellarimplant or component can be selected and/or designed so that it issmaller than one or more of the AP or ML or oblique or other dimensionsin at least a portion of the uncut patella and/or in at least a portionof the patella resection profile. For example, in one or more selectdimensions the patellar implant or component can be selected and/ordesigned to be less than 5%, 10%, 15%, 20%, or other percentage relativeto the patellar profile or resected patellar profile for a givenresection depth. The patellar implant can be selected and/or designed toachieve a desired fit in one or more of those dimensions or otherdimensions so that the fit is applicable to two or more resectiondepths. In this manner, the surgeon has the ability to change hisresection depth intraoperatively, while, for example, still avoidingimplant overhang.

A patellar implant also can be selected or designed, for example, basedon the patient's original patellar surface shape. For example, if thepatellar has a dome shape, a substantially dome shaped implant orcomponent can be selected or designed. If the patella has a relativelyflat shape, a more flat implant or component can be selected ordesigned. If the patella has a relatively spherical shape, a morespherical implant or component can be selected or designed. The patellarimplant or component can be round or elliptical. Other shapes arepossible. The patellar implant or component can be longer laterally thanmedially. The lateral and medial lengths can be matched to the nativepatella. Alternatively, the lateral or medial lengths can be matched tothe patient's trochlea. Alternatively, the lateral or medial lengths canbe matched to the trochlear implant dimensions, which can be patientadapted or standard off the shelf. In this embodiment, a patellar shapecan be selected or designed that closely mimics the patient's originalpatellar shape, for example by following, at least in part, the shape orcontour of the cartilage or subchondral bone or portions thereof, forexample in a median ridge, lateral facet, medial facet, trochlea,trochlear groove, and/or in one or more other dimensions. In instanceswhen the patella has been distorted in shape by arthritic deformity, thepatient's original patellar shape can be derived or estimated based onpatient -specific data, for example, based on data regarding thepatient's surrounding or contralateral biological features and/or ondata regarding the patient's distorted biological features. Mathematicalcomputations can be performed using the data to estimate or derive anapproximate shape. Such mathematical computations can use, for example,patella dimensions, trochlear dimensions or femoral dimensions toestimate the original or a preferred patellar shape. Any of thesedimensions can be matched to a reference database of normal individualsto select a trochlear or patellar shape for any of the implantcomponents. The database can be age matched, gender matched, weightmatched, race matched and/or matched with respect to one or more otherfeatures known in the art.

The patellar implant or component shape can, optionally, also beselected and/or designed based on the patient's trochlear shape or basedon the shape of the trochlear implant profile, e.g. of a total kneeimplant.

The patellar implant or component can be selected based on a singlemeasured or derived parameter. Alternatively, the patellar implant orcomponent can be selected based on multiple parameters, e.g., AP and MLdimensions or AP, ML and oblique dimensions, or AP, ML, and obliquedimensions and desired resection depth, or AP, ML, and obliquedimensions, and/or desired resection depth and/or trochlear shape ortrochlear implant shape. A weighting can be applied to differentparameters. Mathematical or statistical models can be applied forderiving the preferred patellar shape and for designing or selecting animplant based on a multiparametric fit or optimization. These fits oroptimization can include kinematic modeling, estimations andmeasurements.

The resection depth determination can be based on the desired thicknessof the patellar implant or patellar component. For example, theresection depth can be at a distance from the native articulatingsurface patellar cartilage or subchondral bone that is substantiallyequal to the thickness of the patellar implant or component. In anotherembodiment, for example if a femoral component is chosen that removesmore of the patient's trochlear bone and that has, for example, afemoral component trochlear articulating surface that is posterior tothe patient's uncut trochlea, the patellar resection depth may befurther posterior, i.e., less bone is removed from the articulatingsurface the patellar implant or component to extend the patellar implantfurther toward the femur than the native patella. In this instance, thepatellar resection depth can be derived using the following exemplaryapproach:

-   -   1. Start at the patellar articular cartilage or subchondral bone        surface.    -   2. Move resection cut plane into the patella to the point that        it substantially matches the patellar implant/component        thickness.    -   3. Move the resection cut plane back toward the patellar        articular surface (or, in select circumstances anterior) by an        amount sufficient to offset the difference between the femoral        component trochlear articulating surface and the native        trochlear cartilage or subchondral bone surface.

The above embodiments are applicable to patellar implants or componentsthat are designed or derived for a particular patient as well as toimplants that are pre-manufactured and selected based on one or moremeasurements.

The patellar component can be made of a plastic, e.g., a polyethylene, ametal or ceramic. The patellar component can, for example, include ametal backing. The patellar implant can be cemented or uncemented. Thepatellar implant component can be symmetrical or asymmetrical. It can bespherical or aspherical. The patellar implant component can includesymmetric portions and asymmetric portions. For example, the patellarimplant component can be symmetric in the AP dimension and asymmetric inthe ML dimension. The patellar implant component can be round orelliptical. Other shapes are possible. The patellar implant or componentcan be longer laterally than medially.

In certain embodiments, a patella implant or implant component havingone or more patient-specific features is included. In addition oralternatively, certain embodiments include, for example, a patellaimplant or implant component having one or more features that arepatient-optimized (i.e, patient-engineered), e.g., designed based onpatient-specific data to enhance one or more parameters, such as (1)deformity correction and limb alignment; (2) preserving bone, cartilage,or ligaments; (3) preserving and/or optimizing features of the patient'sanatomy such as patella, trochlea and trochlear shape; (4) restoringand/or optimizing joint kinematics or biomechanics includingpatellofemoral tracking, and/or (5) restoring or optimizing joint-linelocation and/or joint gap width. For example, a patella implant orimplant component feature can be patient-optimized or patient-engineeredto enhance the kinematics between the patellar component and the femoralcomponent. The patient-specific and/or patient-optimized patellarimplant features and dimensions described herein can be applied, asappropriate, to either a patellar implant that completely replaces apatient's patella or to a patellar implant that amounts to a resectedsurface of a patient's patella. Embodiments that includepatient-specific and/or patient-optimized aspects also can include oneor more standard aspects, for example a standard bearing surface.

In certain embodiments, one or more features of a patellar implant orimplant component are patient-specific. For example, certain embodimentsof patellar implants can be directed to restoring or maintaining thepatient's original patella thickness in one or more locations, which canhelp to preserve bone and restore patella-femoral (“P-F”) kinematics,for example, by restoring the patient's P-F joint-line. Accordingly, incertain embodiments, the thickness of the patella implant substantiallypositively-matches the thickness of the patient's patella in one or morelocations. Patient-specific images of the patient's joint, for example,from a CT or MRI scan, can be used for this purpose. The scan can beobtained pre-operatively to determine the patient's patellar thicknessincluding at least one of bone and articular cartilage or combinationsthereof in different locations of the patella, e.g., the superior dome,superior third, mid-portion, inferior third, inferior tip, lateralthird, central third, and medial third.

In certain embodiments, patellar implants can be directed to maintainingthe patient's patella surface (e.g., articulating surface) in one ormore locations. Accordingly, in certain embodiments, the surface of thepatella implant substantially positively-matches the surface of thepatient's patella, e.g. cartilage or subchondral bone, in one or morelocations. Certain embodiments of patellar implants can be directed tomaintaining the patient's patella perimeter in one or more planes.Accordingly, in certain embodiments, the perimeter of the patellaimplant substantially positively-matches the uncut or cut perimeter ofthe patient's patella in one or more planes, e.g., for one or moreresection depths. Thus, the implant can be selected or designed toachieve a desired fit or match with the uncut or cut perimeter in one ormore dimensions. Certain embodiments of patellar implants can bedirected to maintaining the patient's patella volume. Accordingly, incertain embodiments, the volume of the patella implant substantiallypositively-matches the volume of the patient's patella. By matching thepatellar dimensions or volume, patellar overstuffing or understuffingcan optionally be avoided. The volume can be adapted by adding orsubtracting based on the shape of the opposing trochlear component. Forexample, if a trochlear component extends anterior to the patient'snative bone, the shape of the patellar component can be adapted so thatthe volume or dimensions are decreased to account for the anteriorextension of the trochlear component. If the trochlear component restsposterior to the native trochlear bone, for example with use of ananterior trochlear bone cut, the shape of the patellar components can beadapted so that the volume or dimensions are increased to account forthe more posterior location of at least portions of the trochlearcomponents. Any of these embodiments can include one or morepatient-specific aspects, patient-engineered aspects, and/or standardaspects.

In certain embodiments, one or more aspects of a patella implant includeone or more patient-optimized features, for example, to optimally engagean engineered or a patient-derived trochlear groove of a femoral implantcomponent. In certain embodiments, a patella implant component caninclude a joint-facing surface that is not derived from a sphere. Forexample, in certain embodiments, the joint-facing surface of a patellaimplant can be derived from a prolate spheroid shape (i.e., an elongatedshape, like a football or lemon), for example, the prolate spheroid cutlongitudinally 5710, as shown in FIG. 57. For example, the top-side ofthe patella implant can be lemon shaped such that it has a differingmedial-lateral versus vertical radius. This design can allow for areduced thickness of the leading edges of the implant duringflexion/extension. In certain embodiments, the apex of a dome-shaped orprolate-shaped outer, joint-surface topography is lateralized relativeto apex of the patient's patella. For example, the patellar implantoptionally can be lateralized 1 mm, 2 mm, 3 mm, 4 mm 5 mm, 1-5 mm,and/or 2-4 mm lateralized. A patella component designed in this way canbe used to address poor ML and/or AP fit of traditional designs and/orrestore the patient's normal patella topography. In addition oralternatively, the thickness of the patella implant can be less thanabout 13 mm, less than about 12 mm, less than about 11 mm, less thanabout 10 mm, less than 9 mm, less than about 8.5 mm, about 8 mm, lessthan about 8 mm, about 7 mm, and/or less than 7 mm. Further aspects ofembodiments of patella implant components are shown in FIGS. 58A-58C.For example, FIG. 58A depicts a patellar implant component (e.g., in anaxial plane) having a sombrero-shaped profile for its surface thatarticulates with the trochlea. As shown, the peak of the articulatingsurface is offset about 2 mm laterally; however, the peak can be offsetlaterally or medially less than about 2 mm (e.g., about 0.5 to 2 mm) orgreater than about 2 mm (e.g., about 2 to 6 mm or about 2 to 4 mm, orabout 2 to 3 mm). The implant component shown in FIG. 58A includes aresection coverage having an elliptical shape and is more similar to atypical anatomical patella as compared to the dome -shaped patella shownin FIG. 58B. FIG. 58B depicts a patellar implant component (e.g., in anaxial plane) having a dome-shaped profile for its surface thatarticulates with the trochlea and includes a resection coverage havingan elliptical shape. This dome-shaped patellar implant component hasenhanced congruence and therefore lower stress and it can tilt and rolleasily in the trochlear groove (i.e., is less constrained). Additionaldetails about embodiments of patellar implant components are shown withreference to FIGS. 58C and 58D. For example, in certain embodiments, thepeak of the dome or other shaped patellar implant component can beoffset laterally or medially by, for example, 1 mm, 2 mm, 3 mm or more.The dome can be symmetric or asymmetric. The shape of the componentperimeter that engages the trochlea can be circular or elongated likethe 2D shape of a football or lemon. The edge between thetrochlea-engaging surface and the patella-engaging surface can be auniform thickness or a non-uniform thickness. For example, the edge canbe thinner on one or both of the proximal and distal edges (e.g., in thedirection of motion) and wider on the medial and/or lateral sides.Exemplary sizes, heights, and edge thicknesses are described in thetable in FIG. 58D. Any of the foregoing is applicable to off-the-shelfimplants that are, for example, selected using one or more parametersthat are measured or derived from an imaging study, or to implants thatare designed for a particular patient.

Certain embodiments are directed to designing, selecting, and/or makinga patellar implant having one or more patient-specific and/orpatient-optimized aspects. For example, a procedure can include one ormore steps of: (a) determining a patellar resection depth; (b)determining the perimeter shape of the resected surface; and (c)selecting, designing and/or making an implant that substantiallypositively-matches, in one or more locations, one or both of theresection depth from (a) and the perimeter shape from (b). One or moreof these steps can be performed preoperatively. The steps optionally canbe varied in sequence. For example, a patellar implant thickness can beselected first, then a resection depth is selected, then, optionally,the perimeter of the implant can be cut or machined or altered to matchthe patellar perimeter in one or more dimensions at the selectedresection depth. Alternatively, a procedure can include one or moresteps of: (a) preoperatively determining a patellar resection depth, forexample based on a trochlear component location and/or a desiredpatellar implant thickness and/or shape; (b) preoperatively determiningthe perimeter shape of the resected surface; (c) optionally selecting ablank implant having a height that substantially positively -matches inone or more locations the resection depth from (a) and having a standardperimeter; and (d) making (e.g., machining, cutting, etc.) the perimeterfor the blank selected in step (c) to substantially positively-match theresected surface determined in step (a), wherein said match can be inone or more dimensions and wherein said match can be a partial or nearcomplete match. One or more of these steps can be performedpreoperatively.

The blank can have different basic features, for example, a dome-shapedarticular surface, a sombrero-shaped articular surface, symmetrically-or asymmetrically-shaped features, spherical or elliptical features,and/or one or more additional basic features, as described above orknown in the art. The step of selecting the blank can also account forthe resultant peripheral or margin thickness of the blank once it is cutfor a given perimeter or a given AP or ML dimension at a desiredresection depth. Thus, for example, a blank can be selected so that onceit is cut the resultant margin thickness does not fall below a desiredminimum material thickness and does not exceed a desired maximalmaterial thickness. Thus, the steps of selecting a blank and cuttingthat blank can include not only adaptations relative to one or moreparameters such as a patient's native anatomy and/or dimensions orkinematics, a resection depth, an implant or component thickness, atrochlear shape, but also a desired minimal and maximal implantthickness in the periphery. Alternatively, a procedure can include oneor more steps of: (a) preoperatively determining a patellar resectiondepth, for example based on a trochlear component location and/or adesired patellar implant thickness and/or shape; (b) preoperativelydetermining the perimeter shape of the resected surface; (c) optionallydesigning an implant having a height that substantiallypositively-matches in one or more locations the resection depth; and (d)making (e.g., machining, cutting, printing, injection molding etc.) theimplant designed in step (c) to substantially positively-match theresected surface determined in step (a), wherein said match can be inone or more dimensions and wherein said match can be a partial or nearcomplete match. One or more of these steps can be performedpreoperatively. FIGS. 59A and 59B show flow charts of exemplaryprocesses for optimizing selecting and/or designing, and optionallyoptimizing, a patellar component based on one or more patient-specificbiological features.

In certain embodiments, the step of (a) determining a patellar resectiondepth can be performed by determining minimal implant material thicknessbased on patient-specific data. For example, patient-specificinformation, such as one or more of weight, activity level, femur size,femur implant aspects such as surface geometry (e.g., trochleargeometry), patellar size, patellar bone decay, femoral shape orgeometry, patellar and/or trochlear and/or femoral kinematics, and otherinformation can be used to determine a minimal implant materialthickness appropriate for the patient. Alternatively or in addition, thestep of (a) determining a patellar resection depth can be determinedbased on the features of one or more resection cuts or other implantcomponents selected for the patient, which have patient-specificfeatures, patient-engineered, or combinations thereof. Then, the patellaresection depth and the patella implant can be designed or selected tomatch this minimal material thickness. Alternatively, once the implantminimal material thickness is determined, a patella implant can beselected from a family of implants having variable thicknesses and thepatellar resection depth is designed to match the thickness of theselected patellar implant. For example, a family of patellar implantscan include implants with thicknesses of two or more of 4 mm, 6 mm, 8mm, 10 mm, 10.5 mm, and 11 mm. FIGS. 56A through 56C illustrate thisprocedure.

In certain embodiments, the step of designing, selecting, and/or making(e.g., cutting from a blank) the implant perimeter to be substantiallypositively-match the determined resected perimeter or a percentagethereof in one or more dimensions can include smoothing the line of thesurface perimeter on the implant, as illustrated in FIGS. 56A and 56C.

Accordingly, certain embodiments are directed to patellar implants andprocedures that include one or more of (a) a preoperatively selectedminimal implant thickness based on patient-specific information, such asfemoral geometry and patellar size, (b) a preoperatively determinedpatellar resection depth that matches the selected minimal implantthickness and/or trochlear component thickness and/or external femoralcomponent trochlea surface, and (c) a perimeter on patellar bone-facingsurface of the implant that substantially positively-matches theperimeter of the resected surface, with optional smoothing of theimplant perimeter. A significant advantage to having matching implantsurface and resected surface perimeters is that it minimizes exposedresected bone and thereby minimizes bleeding, clot formation, and scarformation. Moreover, it can result in more bone preservation and/orimproved kinematics.

In certain embodiments, the patella uses an external shape that isstandard. In this case, the trochlea can also include a standard shape,typically mating with said patellar shape.

In another embodiment, the patellar shape can be standard. The trochlearshape on a patellofemoral replacement or a total knee system can bedesigned or selected to substantially match the patellar implant orcomponent profile in mediolateral direction. The trochlear shape of apatellofemoral replacement or a total knee system can have a standardgeometry in sagittal direction. Alternatively, the sagittal geometry ofthe trochlear surface of the implant can be derived from or adapted tothe patient's sagittal trochlear geometry.

Exemplary combinations are described in Table 12.

TABLE 12 Exemplary patellar and trochlear combinations Patellar MLPatellar AP Trochlea ML Trochlea sagittal Trochlea groove shape shapeshape shape orientation Standard Standard Standard Standard Standard,e.g. substantially sagittal plane or oblique pointing internal orexternal from superior to inferior, straight or curved Standard StandardStandard, e.g. Patient-specific or Standard, e.g. constant coronalpatient derived substantially sagittal curvature plane or obliquepointing internal or external from superior to inferior, straight orcurved Standard Standard Standard Patient-specific or Patient-specificor patient derived patient derived, optionally corrected for trackingabnormalities Patient- Standard Standard Standard Standard, e.g.specific or substantially sagittal patient- plane or oblique pointingderived internal or external from superior to inferior, straight orcurved Standard Patient- Standard Standard Standard, e.g. specific orsubstantially sagittal patient plane or oblique pointing derivedinternal or external from superior to inferior, straight or curvedPatient- Patient- Standard Standard Standard, e.g. specific or specificor substantially sagittal patient patient plane or oblique pointingderived derived internal or external from superior to inferior, straightor curved Standard Patient- Standard Patient-specific orPatient-specific or specific or patient derived patient derived, patientoptionally corrected for derived tracking abnormalities StandardPatient- Standard Patient-specific or Standard, e.g. specific or patientderived substantially sagittal patient plane or oblique pointing derivedinternal or external from superior to inferior, straight or curvedPatient- Standard Patient-specific Standard Patient-specific or specificor or patient patient derived, patient derived optionally corrected forderived tracking abnormalities Patient- Standard Patient-specificStandard Standard, e.g., specific or or patient substantially sagittalpatient derived plane or oblique pointing derived internal or externalfrom superior to inferior, straight or curved Patient- Patient-Patient-specific Patient-specific or Standard, e.g., specific orspecific or or patient patient derived substantially sagittal patientpatient derived plane or oblique pointing derived derived internal orexternal from superior to inferior, straight or curved Patient- Patient-Patient-specific Patient-specific or Patient-specific or specific orspecific or or patient patient derived patient derived, patient patientderived optionally corrected for derived derived tracking abnormalities

The shape and/or dimensions of the trochlea and the selection of atrochlear implant surface or the design of a trochlear implant surfacecan assist in the selection or design of a mating patellar implantand/or implant surface. Alternatively, the shape and/or dimensions of apatella and selected or designed patellar implant can assist in theselection or design of a mating trochlear implant surface and/or shapeand/or dimensions.

A multiparametric fit or optimization can be performed that includes,for example, trochlea shape and/or dimensions, patella fit and/ordimensions, patella implant/component thickness at center and/or rim,patellar component shape, patellar and/or trochlear implant/componentshapes, anterior femoral resection depth, and patellar kinematics inorder to select or design the optimal combination of patellar andtrochlear implant surfaces or components.

As indicated above, in certain embodiments an implant includes apatellar component, a femoral component, and, optionally, a tibialcomponent. As depicted in FIGS. 59A and 59B, one or more features on thefemoral articular surface and/or one or more features on the patellararticular surface can be selected and/or designed based on one or moreof the corresponding component features. For example, one or morefemoral component features, such as trochlear surface contour, trochleargroove width and/or depth, trochlear j -curve, sulcus dimension(s),mediolateral displacement of trochlear groove and/or sulcus (e.g., fromanterior to posterior), medial and/or lateral condylar coronalcurvature(s) along one or more surface sections (e.g., the anteriorsurface section), medial and/or lateral condylar sagittal curvature(s)(j-curves) along one or more sections (e.g., the anterior surfacesection), and/or other features can be selected and/or designed toinclude standard, patient-specific, and/or patient-engineereddimensions. Then, one or more of the patellar component features, suchas the articular surface contour, thickness, perimeter or rim profile,AP distance, ML distance, oblique distance and other features can beselected and/or designed based on one or more of those femoral componentfeatures. Conversely, one or more femoral component features can beselected and/or designed based on one or more of patellar componentfeatures.

For example, the trochlear surface of the femoral component can includeone or more patient-specific features, such as a patient-specifictrochlear j-curve, trochlear groove coronal curvature, and thecorresponding AP dimension(s) of the patellar component and/or itsarticular surface can be selected and/or designed to optimize kinematicfit with the trochlear j-curve. Alternatively or in addition, thetrochlear surface of the femoral component can include one or morepatient-engineered (i.e., patient-optimized) features, such as thetrochlear coronal profile, and the ML dimension of the patellarcomponent and/or its articular surface can be selected and/or designedto optimize kinematic fit with the engineered trochlear coronal profile.

6.3 Tibial Implant Component

In various embodiments described herein, one or more features of atibial implant component are designed and/or selected, optionally inconjunction with an implant procedure, so that the tibial implantcomponent fits the patient. For example, in certain embodiments, one ormore features of a tibial implant component and/or implant procedure aredesigned and/or selected, based on patient-specific data, so that thetibial implant component substantially matches (e.g., substantiallynegatively-matches and/or substantially positively-matches) one or moreof the patient's biological structures. Alternatively or in addition,one or more features of a tibial implant component and/or implantprocedure can be preoperatively engineered based on patient-specificdata to provide to the patient an optimized fit with respect to one ormore parameters, for example, one or more of the parameters describedabove. For example, in certain embodiments, an engineered bonepreserving tibial implant component can be designed and/or selectedbased on one or more of the patient's joint dimensions as seen, forexample, on a series of two-dimensional images or a three-dimensionalrepresentation generated, for example, from a CT scan or MRI scan.Alternatively or in addition, an engineered tibial implant component canbe designed and/or selected, at least in part, to provide to the patientan optimized fit with respect to the engaging, joint-facing surface of acorresponding femoral implant component.

Certain embodiments include a tibial implant component having one ormore patient-adapted (e.g., patient-specific or patient-engineered)features and, optionally, one or more standard features. Optionally, theone or more patient-adapted features can be designed and/or selected tofit the patient's resected tibial surface. For example, depending on thepatient's anatomy and desired postoperative geometry or alignment, apatient's lateral and/or medial tibial plateaus may be resectedindependently and/or at different depths, for example, so that theresected surface of the lateral plateau is higher (e.g., 1 mm, greaterthan 1 mm, 2 mm, and/or greater than 2 mm higher) or lower (e.g., 1 mm,greater than 1 mm, 2 mm, and/or greater than 2 mm lower) than theresected surface of the medial tibial plateau.

Accordingly, in certain embodiments, tibial implant components can beindependently designed and/or selected for each of the lateral and/ormedial tibial plateaus. For example, the perimeter of a lateral tibialimplant component and the perimeter of a medial tibial implant componentcan be independently designed and/or selected to substantially match theperimeter of the resection surfaces for each of the lateral and medialtibial plateaus.

FIGS. 60A and 60B show exemplary unicompartmental medial and lateraltibial implant components without (FIG. 60A) and with (FIG. 60B) apolyethylene layer or insert. As shown, the lateral tibial implantcomponent and the medial tibial implant component have differentperimeters shapes, each of which substantially matches the perimeter ofthe corresponding resection surface (see arrows). In addition, thepolyethylene layers or inserts 6010 for the lateral tibial implantcomponent and the medial tibial implant component have perimeter shapesthat correspond to the respective implant component perimeter shapes. Incertain embodiments, one or both of the implant components can be madeentirely of a plastic or polyethylene (rather than having a having apolyethylene layer or insert) and each entire implant component caninclude a perimeter shape that substantially matches the perimeter ofthe corresponding resection surface.

Moreover, the height of a lateral tibial implant component and theheight of a medial tibial implant component can be independentlydesigned and/or selected to maintain or alter the relative heightsgenerated by different resection surfaces for each of the lateral andmedial tibial plateaus. For example, the lateral tibial implantcomponent can be thicker (e.g., 1 mm, greater than 1 mm, 2 mm, and/orgreater than 2 mm thicker) or thinner (e.g., 1 mm, greater than 1 mm, 2mm, and/or greater than 2 mm thinner) than the medial tibial implantcomponent to maintain or alter, as desired, the relative height of thejoint-facing surface of each of the lateral and medial tibial implantcomponents. As shown in FIG. 60A and FIG. 60B, the relative heights ofthe lateral and medial resection surfaces 6020 is maintained usinglateral and medial implant components (and lateral and medialpolyethylene layers or inserts) that have the same thickness.Alternatively, the lateral implant component (and/or the lateralpolyethylene layer or insert) can have a different thickness than themedial implant component (and/or the medial polyethylene layer orinsert). For embodiments having one or both of the lateral and medialimplant components made entirely of a plastic or polyethylene (ratherthan having a having a polyethylene layer or insert) the thickness ofone implant component can be different from the thickness of the otherimplant component.

Different medial and lateral tibial cut heights also can be applied witha one piece implant component, e.g., a monolithically formed, tibialimplant component. In this case, the tibial implant component and thecorresponding resected surface of the patient's femur can have an angledsurface or a step cut connecting the medial and the lateral surfacefacets. For example, FIGS. 61A to 61C depict three different types ofstep cuts separating medial and lateral resection cut facets on apatient's proximal tibia. In certain embodiments, the bone-facingsurface of the tibial implant component is selected and/or designed tomatch these surface depths and the step cut angle, as well as otheroptional features such as perimeter shape.

Tibial components also can include the same medial and lateral cutheight.

In certain embodiments, the medial tibial plateau facet can be orientedat an angle different than the lateral tibial plateau facet or it can beoriented at the same angle. One or both of the medial and the lateraltibial plateau facets can be at an angle that is patient -specific, forexample, similar to the original slope or slopes of the medial and/orlateral tibial plateaus, for example, in the sagittal plane. Moreover,the medial slope can be patient-specific, while the lateral slope isfixed or preset or vice versa, as exemplified in Table 13.

TABLE 13 Exemplary designs for tibial slopes LATERAL SIDE MEDIAL SIDEIMPLANT SLOPE IMPLANT SLOPE Patient-matched to medial plateauPatient-matched to lateral plateau Patient-matched to medial plateauPatient-matched to medial plateau Patient-matched to lateral plateauPatient-matched to lateral plateau Patient-matched to medial plateau Notpatient-matched, e.g., preset, fixed or intraoperatively adjustedPatient-matched to lateral plateau Not patient-matched, e.g., preset,fixed or intraoperatively adjusted Not patient matched, e.g. preset,Patient-matched to lateral plateau fixed or intraoperatively adjustedNot patient matched, e.g., preset, Patient-matched to medial plateaufixed or intraoperatively adjusted Not patient matched, e.g. preset, Notpatient-matched, e.g. preset, fixed or intraoperatively adjusted fixedor intraoperatively adjusted

The exemplary combinations described in Table 13 are applicable toimplants that use two unicompartmental tibial implant components with orwithout metal backing, one medial and one lateral. They also can beapplicable to implant systems that use a single tibial implant componentincluding all plastic designs or metal backed designs with inserts(optionally a single insert for the medial and lateral plateau, or twoinserts, e.g., one medial and one lateral), for example PCL retaining,posterior stabilized, or ACL and PCL retaining implant components. Theslope preferably is between 0 and 7 degrees, but other embodiments withother slope angles outside that range can be used. The slope can varyacross one or both tibial facets from anterior to posterior. Forexample, a lesser slope, e.g. 0-1 degrees, can be used anteriorly, and agreater slope can be used posteriorly, for example, 4-5 degrees.Variable slopes across at least one of a medial or a lateral tibialfacet can be accomplished, for example, with use of burrs (for exampleguided by a robot) or with use of two or more bone cuts on at least oneof the tibial facets. In certain embodiments, two separate slopes can beused medially and laterally. Independent tibial slope designs can beuseful for achieving bone preservation. In addition, independent slopedesigns can be advantageous in achieving implant kinematics that will bemore natural, closer to the performance of a normal knee or thepatient's knee.

In certain embodiments, the slope can be fixed, e.g. at 3, 5 or 7degrees in the sagittal plane. In certain embodiments, the slope, eithermedial or lateral or both, can be patient-specific. The patient's medialslope can be used to derive the medial tibial component slope and,optionally, the lateral component slope, in either a single or atwo-piece tibial implant component. The patient's lateral slope can beused to derive the lateral tibial component slope and, optionally, themedial component slope, in either a single or a two-piece tibial implantcomponent. A patient's slope typically is between 0 and 7 degrees. Inselect instances, a patient may show a medial or a lateral slope that isgreater than 7 degrees. In this case, if the patient's medial slope hasa higher value than 7 degrees or some other pre-selected threshold, thepatient's lateral slope can be applied to the medial tibial implantcomponent or to the medial side of a single tibial implant component. Ifthe patient's lateral slope has a higher value than 7 degrees or someother pre-selected threshold, the patient's medial slope can be appliedto the lateral tibial implant component or to the lateral side of asingle tibial implant component. Alternatively, if the patient's slopeon one or both medial and lateral sides exceeds a pre-selected thresholdvalue, e.g., 7 degrees or 8 degrees or 10 degrees, a fixed slope can beapplied to the medial component or side, to the lateral component orside, or both. The fixed slope can be equal to the threshold value,e.g., 7 degrees or it can be a different value. FIGS. 62A and 62B showexemplary flow charts for deriving a medial tibial component slope (FIG.62A) and/or a lateral tibial component slope (FIG. 62B) for a tibialimplant component.

A fixed tibial slope can be used in any of the embodiments describedherein.

In another embodiment, a mathematical function can be applied to derivea medial implant slope and/or a lateral implant slope, or both (whereinboth can be the same). In certain embodiments, the mathematical functioncan include a measurement derived from one or more of the patient'sjoint dimensions as seen, for example, on a series of two -dimensionalimages or a three-dimensional representation generated, for example,from a CT scan or MRI scan. For example, the mathematical function caninclude a ratio between a geometric measurement of the patient's femurand the patient's tibial slope. Alternatively or in addition, themathematical function can be or include the patient's tibial slopedivided by a fixed value. In certain embodiments, the mathematicalfunction can include a measurement derived from a corresponding implantcomponent for the patient, for example, a femoral implant component,which itself can include patient-specific, patient-engineered, and/orstandard features. Many different possibilities to derive the patient'sslope using mathematical functions can be applied by someone skilled inthe art.

In certain embodiments, the medial and lateral tibial plateau can beresected at the same angle. For example, a single resected cut or thesame multiple resected cuts can be used across both plateaus. In otherembodiments, the medial and lateral tibial plateau can be resected atdifferent angles. Multiple resection cuts can be used when the medialand lateral tibial plateaus are resected at different angles.Optionally, the medial and the lateral tibia also can be resected at adifferent distance relative to the tibial plateau. In this setting, thetwo horizontal plane tibial cuts medially and laterally can havedifferent slopes and/or can be accompanied by one or two vertical oroblique resection cuts, typically placed medial to the tibial plateaucomponents. FIG. 16 and FIGS. 61A to 61C show several exemplary tibialresection cuts, which can be used in any combination for the medial andlateral plateaus.

The medial tibial implant component plateau can have a flat, convex,concave, or dished surface and/or it can have a thickness different thanthe lateral tibial implant component plateau. The lateral tibial implantcomponent plateau can have a flat, convex, concave, or dished surfaceand/or it can have a thickness different than the medial tibial implantcomponent plateau. The different thickness can be achieved using adifferent material thickness, for example, metal thickness orpolyethylene or insert thickness on either side. In certain embodiments,the lateral and medial surfaces are selected and/or designed to closelyresemble the patient's anatomy prior to developing the arthritic state.

The height of the medial and/or lateral tibial implant componentplateau, e.g., metal only, ceramic only, metal backed with polyethyleneor other insert, with single or dual inserts and single or dual trayconfigurations can be determined based on the patient's tibial shape,for example using an imaging test.

Alternatively, the height of the medial and/or lateral tibial componentplateau, e.g. metal only, ceramic only, metal backed with polyethyleneor other insert, with single or dual inserts and single or dual trayconfigurations can be determined based on the patient's femoral shape.For example, if the patient's lateral condyle has a smaller radius thanthe medial condyle and/or is located more superior than the medialcondyle with regard to its bearing surface, the height of the tibialcomponent plateau can be adapted and/or selected to ensure an optimalarticulation with the femoral bearing surface. In this example, theheight of the lateral tibial component plateau can be adapted and/orselected so that it is higher than the height of the medial tibialcomponent plateau. Since polyethylene is typically not directly visibleon standard x-rays, metallic or other markers can optionally be includedin the inserts in order to indicate the insert location or height, inparticular when asymmetrical medial and lateral inserts or inserts ofdifferent medial and lateral thickness are used.

Alternatively, the height of the medial and/or lateral tibial componentplateau, e.g. metal only, ceramic only, metal backed with polyethyleneor other insert, with single or dual inserts and single or dual trayconfigurations can be determined based on the shape of a correspondingimplant component, for example, based on the shape of certain featuresof the patient's femoral implant component. For example, if the femoralimplant component includes a lateral condyle having a smaller radiusthan the medial condyle and/or is located more superior than the medialcondyle with regard to its bearing surface, the height of the tibialimplant component plateaus can be adapted and/or selected to ensure anoptimal articulation with the bearing surface(s) of the femoral implantcomponent. In this example, the height of the lateral tibial implantcomponent plateau can be adapted and/or selected to be higher than theheight of the medial tibial implant component plateau.

Moreover, the surface shape, e.g. mediolateral or anteroposteriorcurvature or both, of the tibial insert(s) can reflect the shape of thefemoral component. For example, the medial insert shape can be matchedto one or more radii on the medial femoral condyle of the femoralcomponent. The lateral insert shape can be matched to one or more radiion the lateral femoral condyle of the femoral component. The lateralinsert may optionally also be matched to the medial condyle. Thematching can occur, for example, in the coronal plane. This has benefitsfor wear optimization. A pre-manufactured insert can be selected for amedial tibia that matches the medial femoral condyle radii in thecoronal plane with a pre-selected ratio, e.g. 1:5 or 1:7 or 1:10. Anycombination is possible. A pre-manufactured insert can be selected for alateral tibia that matches the lateral femoral condyle radii in thecoronal plane with a pre-selected ratio, e.g. 1:5 or 1:7 or 1:10. Anycombination is possible. Alternatively, a lateral insert can also bematched to a medial condyle or a medial insert shape can also be matchedto a lateral condyle. These combinations are possible with single anddual insert systems with metal backing. Someone skilled in the art willrecognize that these matchings can also be applied to implants that useall polyethylene tibial components; i.e. the radii on all polyethylenetibial components can be matched to the femoral radii in a similarmanner.

The matching of radii can also occur in the sagittal plane. For example,a cutter can be used to cut a fixed coronal curvature into a tibialinsert or all polyethylene tibia that is matched to or derived from afemoral implant or patient geometry. The path and/or depth that thecutter is taking can be driven based on the femoral implant geometry orbased on the patient's femoral geometry prior to the surgery. Medial andlateral sagittal geometry can be the same on the tibial inserts or allpoly tibia. Alternatively, each can be cut separately. By adapting ormatching the tibial poly geometry to the sagittal geometry of thefemoral component or femoral condyle, a better functional result may beachieved. For example, more physiologic tibiofemoral motion andkinematics can be enabled.

The medial and/or the lateral component can include a trough. The medialcomponent can be dish shaped, while the lateral component includes atrough. The lateral component can be dish shaped, while the medialcomponent includes a trough. The lateral component can be convex, whilethe medial component includes a trough. The shape of the medial orlateral component can be patient derived or patient matched in one, twoor three dimensions, for example as it pertains to its perimeter as wellas its surface shape. The convex shape of the lateral component can bepatient derived or patient matched in one, two or three dimensions. Thetrough can be straight. The trough can also be curved. The curvature ofthe trough can have a constant radius of curvature or it can includeseveral radii of curvature. The radii can be patient matched or patientderived, for example based on the femoral geometry or on the patient'skinematics. These designs can be applied with a single -piece tibialpolyethylene or other plastic insert or with two-piece tibialpolyethylene or other plastic inserts. FIGS. 63A through 63J showexemplary combinations of tibial tray designs. FIGS. 64A through 64Finclude additional embodiments of tibial implant components that arecruciate retaining.

The perimeter of the tibial component, metal backed, optionally polyinserts, or all plastic or other material, can be matched to or derivedfrom the patient's tibial shape, and can be optimized for different cutheights and/or tibial slopes. In a preferred embodiment, the shape ismatched to the cortical bone of the cut surface. The surface topographyof the tibial bearing surface can be designed or selected to match orreflect at least a portion of the tibial geometry, in one or moreplanes, e.g., a sagittal plane or a coronal plane, or both. The medialtibial implant surface topography can be selected or designed to matchor reflect all or portions of the medial tibial geometry in one or moreplanes, e.g., sagittal and coronal. The lateral tibial implant surfacetopography can be selected or designed to match or reflect all orportions of the lateral tibial geometry in one or more planes, e.g.,sagittal and coronal. The medial tibial implant surface topography canbe selected or designed to match or reflect all or portions of thelateral tibial geometry in one or more planes, e.g., sagittal andcoronal. The lateral tibial implant surface topography can be selectedor designed to match or reflect all or portions of the medial tibialgeometry in one or more planes, e.g., sagittal and coronal.

The surface topography of the tibial bearing surface(s) can be designedor selected to match or reflect at least portions of the femoralgeometry or femoral implant geometry, in one or more planes, e.g., asagittal plane or a coronal plane, or both. The medial implant surfacetopography can be selected or designed to match or reflect all orportions of the medial femoral geometry or medial femoral implantgeometry in one or more planes. The lateral implant surface topographycan be selected or designed to match or reflect all or portions of thelateral femoral geometry or lateral femoral implant geometry in one ormore planes. The medial implant surface topography can be selected ordesigned to match or reflect all or portions of the lateral femoralgeometry or lateral femoral implant geometry in one or more planes. Thelateral implant surface topography can be selected or designed to matchor reflect all or portions of the medial femoral geometry or medialfemoral implant geometry in one or more planes. The medial and/or thelateral surface topography can be fixed in one, two or all dimensions.The latter can typically be used when at least one femoral geometry,e.g., the coronal curvature, is also fixed.

The implant surface topography can include one or more of the following:

-   -   Curvature of convexity in sagittal plane, optionally patient        derived or matched, e.g., based on tibial or femoral geometry    -   Curvature of convexity in coronal plane, optionally patient        derived or matched, e.g., based on tibial or femoral geometry    -   Curvature of concavity in sagittal plane, optionally patient        derived or matched, e.g., based on tibial or femoral geometry    -   Curvature of concavity in coronal plane, optionally patient        derived or matched, e.g., based on tibial or femoral geometry    -   Single sagittal radius of curvature, optionally patient derived        or matched, e.g., based on tibial or femoral geometry    -   Multiple sagittal radii of curvature, optionally patient derived        or matched, e.g., based on tibial or femoral geometry    -   Single coronal radius of curvature, optionally patient derived        or matched, e.g., based on tibial or femoral geometry    -   Multiple coronal radii of curvature, optionally patient derived        or matched, e.g., based on tibial or femoral geometry    -   Depth of dish, optionally patient derived or matched, e.g.,        based on tibial or femoral geometry    -   AP length of dish, optionally patient derived or matched, e.g.,        based on tibial or femoral geometry    -   ML width of dish, optionally patient derived or matched, e.g.,        based on tibial or femoral geometry    -   Depth of trough, optionally patient derived or matched, e.g.,        based on tibial or femoral geometry    -   AP length of trough, optionally patient derived or matched,        e.g., based on tibial or femoral geometry    -   ML width of trough, optionally patient derived or matched, e.g.,        based on tibial or femoral geometry    -   Curvature of trough, optionally patient derived or matched,        e.g., based on tibial or femoral geometry

All of the tibial designs discussed can be applied with a:

-   -   single piece tibial polyethylene insert, for example with a        single metal backed component    -   single piece tibial insert of other materials, for example with        a single metal backed component    -   two piece tibial polyethylene inserts, for example with a single        metal backed component    -   two piece tibial inserts of other materials, for example with a        single metal backed component        -   single piece all polyethylene tibial implant        -   two piece all polyethylene tibial implant, e.g. medial and            lateral        -   single piece metal tibial implant (e.g., metal on metal or            metal on ceramic)        -   two piece metal tibial implant, e.g., medial and lateral            (e.g., metal on metal or metal on ceramic)        -   single piece ceramic tibial implant        -   two piece ceramic tibial implant, e.g., medial and lateral

Any material or material combination currently known in the art anddeveloped in the future can be used.

Certain embodiments of tibial trays can have the following features,although other embodiments are possible: modular insert system(polymer); cast cobalt chrome; standard blanks (cobalt portion and/ormodular insert) can be made in advance, then shaped patient-specific toorder; thickness based on size (saves bone, optimizes strength);allowance for 1-piece or 2-piece insert systems; and/or different medialand lateral fins.

In certain embodiments, the tibial tray is designed or cut from a blankso that the tray periphery matches the edge of the cut tibial bone, forexample, the patient-matched peripheral geometryachieves >70%, >80%, >90%, or >95% cortical coverage. In certainembodiments, the tray periphery is designed to have substantially thesame shape, but be slightly smaller, than the cortical area.

The patient-adapted tibial implants of certain embodiments allow fordesign flexibility. For example, inserts can be designed to complimentan associated condyle of a corresponding femoral implant component, andcan vary in dimensions to optimize design, for example, one or more ofheight, shape, curvature (preferably flat to concave), and location ofcurvature to accommodate natural or engineered wear pattern.

In the knee, a tibial cut can be selected so that it is, for example, 90degrees perpendicular to the tibial mechanical axis or to the tibialanatomical axis. The cut can be referenced, for example, by finding theintersect with the lowest medial or lateral point on the plateau.

The slope for tibial cuts typically is between 0 and 7 or 0 and 8degrees in the sagittal plane. Rarely, a surgeon may elect to cut thetibia at a steeper slope. The slope can be selected or designed into apatient-specific cutting jig using a preoperative imaging test. Theslope can be similar to the patient's preoperative slope on at least oneof a medial or one of a lateral side. The medial and lateral tibia canbe cut with different slopes. The slope also can be different from thepatient's preoperative slope on at least one of a medial or one of alateral side.

The tibial cut height can differ medially and laterally, as shown inFIG. 16 and FIGS. 61A to 61C. In some patients, the uncut lateral tibiacan be at a different height, for example, higher or lower, than theuncut medial tibia. In this instance, the medial and lateral tibial cutscan be placed at a constant distance from the uncut medial and the uncutlateral tibial plateau, resulting in different cut heights medially orlaterally. Alternatively, they can be cut at different distancesrelative to the uncut medial and lateral tibial plateau, resulting inthe same cut height on the remaining tibia. Alternatively, in thissetting, the resultant cut height on the remaining tibia can be electedto be different medially and laterally. In certain embodiments,independent design of the medial and lateral tibial resection heights,resection slopes, and/or implant component (e.g., tibial tray and/ortibial tray insert), can enhance bone perseveration on the medial and/orlateral sides of the proximal tibia as well as on the opposing femoralcondyles.

In certain embodiments, a patient-specific proximal tibia cut (and thecorresponding bone-facing surface of the tibial component) is designedby: (1) finding the tibial axis perpendicular plane (“TAPP”); (2)lowering the TAPP, for example, 2 mm below the lowest point of themedial tibial plateau; (3) sloping the lowered TAPP 5 degreesposteriorly (no additional slope is required on the proximal surface ofthe insert); (4) fixing the component posterior slope, for example, at 5degrees; and (5) using the tibial anatomic axis derived from Cobb orother measurement technique for tibial implant rotational alignment. Asshown in FIG. 65, resection cut depths deeper than 2 mm below the lowestpoint of the patient's uncut medial or lateral plateau (e.g., medialplateau) may be selected and/or designed, for example, if the patient'sanatomy includes an abnormality or diseased tissue below this point, orif the surgeon prefers a lower cut. For example, resection cut depths of2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or 5 mm can be selected and/ordesigned and, optionally, one or more corresponding tibial and/orfemoral implant thicknesses can be selected and/or designed based onthis patient-specific information.

In certain embodiments, a patient-specific proximal tibial cut (and thecorresponding bone-facing surface of the tibial component) uses thepreceding design except for determining the A-P slope of the cut. Incertain embodiments, a patient-specific A-P slope can be used, forexample, if the patient's anatomic slope is between 0 degrees and 7degrees, or between 0 degrees and 8 degrees, or between 0 degrees and 9degrees; a slope of 7 degrees can be used if the patient's anatomicslope is between 7 degrees and 10 degrees, and a slope of 10° can beused if the patient's anatomic slope is greater than 10 degrees.

In certain embodiments, a patient-specific A-P slope is used if thepatient's anatomic slope is between 0 and 7 degrees and a slope of 7degrees is used if the patient's anatomic slope is anything over 7degrees. Someone skilled in the art will recognize other methods fordetermining the tibial slope and for adapting it during implant and jigdesign to achieve a desired implant slope.

A different tibial slope can be applied on the medial and the lateralside. A fixed slope can be applied on one side, while the slope on theother side can be adapted based on the patient's anatomy. For example, amedial slope can be fixed at 5 degrees, while a lateral slope matchesthat of the patient's tibia. In this setting, two unicondylar tibialinserts or trays can be used. Alternatively, a single tibial component,optionally with metal backing, can be used wherein said component doesnot have a flat, bone-facing surface, but includes, for example, anoblique portion to connect the medial to the lateral side substantiallynegatively-match resected lateral and medial tibial surfaces as shown,for example, in FIG. 16 and FIGS. 61A to 61C.

In certain embodiments, the axial profile (e.g., perimeter shape) of thetibial implant can be designed to match the axial profile of thepatient's cut tibia, for example as described in U.S. Patent ApplicationPublication No. 2009/0228113. Alternatively or in addition, in certainembodiments, the axial profile of the tibial implant can be designed tomaintain a certain percentage or distance in its perimeter shaperelative to the axial profile of the patient's cut tibia. Alternativelyor in addition, in certain embodiments, the axial profile of the tibialimplant can be designed to maintain a certain percentage or overhang inits perimeter shape relative to the axial profile of the patient's cuttibia.

Any of the tibial implant components described above can be derived froma blank that is cut to include one or more patient-specific features.

Tibial tray designs can include patient-specific, patient-engineered,and/or standard features. For example, in certain embodiments the tibialtray can have a front-loading design that requires minimal impactionforce to seat it. The trays can come in various standard or standardblank designs, for example, small, medium and large standard or standardblank tibial trays can be provided. FIG. 66 shows exemplary small,medium and large blank tibial trays. As shown, the tibial trayperimeters include a blank perimeter shape that can be designed based onthe design of the patient's resected proximal tibia surface. In certainembodiments, small and medium trays can include a base thickness of 2 mm(e.g., such that a patient's natural joint line may be raised 3-4 mm ifthe patient has 2-3 mm of cartilage on the proximal tibia prior to thedisease state). Large trays can have a base thickness of 3 mm (such thatin certain embodiments it may be beneficial to resect an additional 1 mmof bone so that the joint line is raised no more than 2-3 mm (assuming2-3 mm of cartilage on the patient's proximal tibia prior to the diseasestate).

A patient-specific peg alignment (e.g., either aligned to the patient'smechanical axis or aligned to another axis) can be combined with apatient-specific A-P cut plane. For example, in certain embodiments thepeg alignment can tilt anteriorly at the same angle that the A-P slopeis designed. In certain embodiments, the peg can be aligned in relationto the patient's sagittal mechanical axis, for example, at apredetermined angle relative to the patient's mechanical axis. FIG. 67shows exemplary A-P and peg angles for tibial trays.

The joint-facing surface of a tibial implant component includes a medialbearing surface and a lateral bearing surface. Like the femoral implantbearing surface(s) described above, a bearing surface on a tibialimplant (e.g., a groove or depression or a convex portion (on thelateral side) in the tibial surface that receives contact from a femoralcomponent condyle) can be of standard design, for example, available in6 or 7 different shapes, with a single radius of curvature or multipleradii of curvature in one dimension or more than one dimension.Alternatively, a bearing surface can be standardized in one or moredimensions and patient-adapted in one or more dimensions. A singleradius of curvature and/or multiple radii of curvature can be selectedin one dimension or multiple dimensions. Some of the radii can bepatient-adapted.

Each of the two contact areas of the polyethylene insert of the tibialimplant component that engage the femoral medial and lateral condylesurfaces can be any shape, for example, convex, flat, or concave, andcan have any radii of curvature. In certain embodiments, any one or moreof the curvatures of the medial or lateral contact areas can includepatient-specific radii of curvature. Specifically, one or more of thecoronal curvature of the medial contact area, the sagittal curvature ofthe medial contact area, the coronal curvature of the lateral contactarea, and/or the sagittal curvature of the lateral contact area caninclude, at least in part, one or more patient-specific radii ofcurvature. In certain embodiments, the tibial implant component isdesigned to include one or both medial and lateral bearing surfaceshaving a sagittal curvature with, at least in part, one or more patient-specific radii of curvature and a standard coronal curvature. Incertain embodiments, the bearing surfaces on one or both of the medialand lateral tibial surfaces can include radii of curvature derived from(e.g., the same length or slightly larger, such as 0-10% larger than)the radii of curvature on the corresponding femoral condyle. Havingpatient-adapted sagittal radii of curvature, at least in part, can helpachieve normal kinematics with full range of motion.

Alternatively, the coronal curvature can be selected, for example, bychoosing from a family of standard curvatures the one standard curvaturehaving the radius of curvature or the radii of curvature that is mostsimilar to the coronal curvature of the patient's uncut femoral condyleor that is most similar to the coronal curvature of the femoral implantcomponent.

In preferred embodiments, one or both tibial medial and lateral contactareas have a standard concave coronal radius that is larger, for exampleslightly larger, for example, between 0 and 1 mm, between 0 and 2 mm,between 0 and 4 mm, between 1 and 2 mm, and/or between 2 and 4 mmlarger, than the convex coronal radius on the corresponding femoralcomponent. By using a standard or constant coronal radius on a femoralcondyle with a matching standard or constant coronal radius or slightlylarger on a tibial insert, for example, with a tibial radius ofcurvature of from about 1.05× to about 2×, or from about 1.05× to about1.5×, or from about 1.05× to about 1.25×, or from about 1.05× to about1.10×, or from about 1.05× to about 1.06×, or about 1.06× of thecorresponding femoral implant coronal curvature. The relative convexfemoral coronal curvature and slightly larger concave tibial coronalcurvature can be selected and/or designed to be centered to each aboutthe femoral condylar centers.

In the sagittal plane, one or both tibial medial and lateral concavecurvatures can have a standard curvature slightly larger than thecorresponding convex femoral condyle curvature, for example, between 0and 1 mm, between 0 and 2 mm, between 0 and 4 mm, between 1 and 2 mm,and/or between 2 and 4 mm larger, than the convex sagittal radius on thecorresponding femoral component. For example, the tibial radius ofcurvature for one or both of the medial and lateral sides can be fromabout 1.1× to about 2×, or from about 1.2× to about 1.5×, or from about1.25× to about 1.4×, or from about 1.30× to about 1.35×, or about 1.32×of the corresponding femoral implant sagittal curvature. In certainembodiments, the depth of the curvature into the tibial surface materialcan depend on the height of the surface into the joint gap. Asmentioned, the height of the medial and lateral tibial component joint-facing surfaces can be selected and/or designed independently. Incertain embodiments, the medial and lateral tibial heights are selectedand/or designed independently based on the patient's medial and lateralcondyle height difference. In addition or alternatively, in certainembodiments, a threshold minimum or maximum tibial height and/or tibialinsert thickness can be used. For example, in certain embodiments, athreshold minimum insert thickness of 6 mm is employed so that no lessthan a 6 mm medial tibial insert is used.

By using a tibial contact surface sagittal and/or coronal curvatureselected and/or designed based on the curvature(s) of the correspondingfemoral condyles or a portion thereof (e.g., the bearing portion), thekinematics and wear of the implant can be optimized. For example, thisapproach can enhance the wear characteristics a polyethylene tibialinsert. This approach also has some manufacturing benefits.

For example, a set of different-sized tools can be produced wherein eachtool corresponds to one of the pre-selected standard coronal curvatures.The corresponding tool then can be used in the manufacture of apolyethylene insert of the tibial implant component, for example, tocreate a curvature in the polyethylene insert. FIG. 68A shows sixexemplary tool tips 6810 and a polyethylene insert 6820 in cross-sectionin the coronal view. The size of the selected tool can be used togenerate a polyethylene insert having the desired coronal curvature. Inaddition, FIG. 68A shows an exemplary polyethylene insert having twodifferent coronal curvatures created by two different tool tips. Theaction of the selected tool on the polyethylene insert, for example, asweeping arc motion by the tool at a fixed point above the insert, canbe used to manufacture a standard or patient-specific sagittalcurvature.

FIG. 68B shows a sagittal view of two exemplary tools 6830, 6840sweeping from different distances into the polyethylene insert 6820 of atibial implant component to create different sagittal curvatures in thepolyethylene insert 6820.

In certain embodiments, one or both of the tibial contact areas includesa concave groove having an increasing or decreasing radius along itssagittal axis, for example, a groove with a decreasing radius fromanterior to posterior.

As shown in FIG. 69A, in certain embodiments the shape of the concavegroove 6910 on the lateral and/or on the medial sides of thejoint-facing surface of the tibial insert 6920 can be matched by aconvex shape 6930 on the opposing side surface of the insert and,optionally, by a concavity 6940 on the engaging surface of the tibialtray 6950. This can allow the thickness of the component to remainconstant 6960, even though the surfaces are not flat, and thereby canhelp maintain a minimum thickness of the material, for example, plasticmaterial such as polyethylene. For example, an implant insert canmaintain a constant material thickness (e.g., less than 5.5 mm, 5.5 mm,5.6 mm, 5.7 mm, 5.8 mm, 5.9 mm, 6.0 mm, 6.1 mm, or greater than 6.1 mm)even though the insert includes a groove on the joint-facing surface.The constant material thickness can help to minimize overall minimumimplant thickness while achieving or maintaining a certain mechanicalstrength (as compared to a thicker implant). The matched shape on themetal backing can serve the purpose of maintaining a minimumpolyethylene thickness. It can, however, also include design features toprovide a locking mechanism between the polyethylene or other insert andthe metal backing. Such locking features can include ridges, edges, oran interference fit. In the case of an interference fit, thepolyethylene can have slightly larger dimensions at the undersurfaceconvexity than the matching concavity on the metal tray. This can bestabilized against rails or dove tail locking mechanisms in the centeror the sides of the metal backing. Other design options are possible.For example, the polyethylene extension can have a saucer shape that cansnap into a matching recess on the metal backing. In addition, as shownin FIG. 69A, any corresponding pieces of the component, such as a metaltray, also can include a matching groove to engage the curved surface ofthe plastic material. Two exemplary concavity dimensions are shown inFIG. 69B. As shown in the figure, the concavities or scallops havedepths of 1.0 and 0.7 mm, based on a coronal geometry of R42.4 mm. At a1.0 mm depth, the footprint width is 18.3 mm. At a 0.70 mm depth, thefootprint width is 15.3 mm. These dimensions are only of exemplarynature. Many other configurations are possible.

In certain embodiments, the sagittal curvature of the femoral componentcan be designed to be tilted, as suggested by FIG. 70. The correspondingcurvature of the tibial surface can be tilted by that same slope, whichcan allow for thicker material on the corresponding tibial implant, forexample, thicker poly at the anterior or posterior aspect of the tibialimplant. The femoral component J-curve, and optionally the correspondingcurvature for the tibial component, can be tilted by the same slope inboth the medial and lateral condyles, just in the medial condyle or justin the lateral condyle or both independently or coupled. In certainembodiments, some additional material can be removed or the materialthickness can be adapted from the posterior aspect of the femoral and/ortibial curvatures to allow for rotation.

In addition to the implant component features described above, certainembodiments can include features and designs for cruciate substitution.These features and designs can include, for example, a keel, post, orprojection that projects from the bone-facing surface of the tibialimplant component to engage on the corresponding an intercondylarhousing, receptacle, or bars on the corresponding femoral implantcomponent.

FIGS. 49A and 49B, 50A and 50B, 51, and 52A through 52P depict variousfeatures of intercondylar bars or in intercondylar housing for acruciate-substituting femoral implant component. In addition, FIGS. 50Aand 50B show a tibial implant component having a post or projection thatcan be used in conjunction with an intercondylar housing, receptacle,and/or bars on a femoral implant component as a substitute for apatient's PCL″, which may be sacrificed during the implant procedure.Specifically, the post or projection on the tibial component engages theintercondylar housing, receptacle or bars on the femoral implantcomponent to stabilize the joint during flexion, particular during highflexion.

FIGS. 71A and 71B depict exemplary cross-sections of tibial implantcomponents having a post (or keel or projection) projecting from thebone-facing surface of the implant component. In particular, FIG. 71Ashows (a) a tibial implant component with a straight post or projectionand (b)-(d) tibial implant components having posts or projectionsoriented laterally, with varying thicknesses, lengths, and curvatures.FIG. 71B shows (a)-(e) tibial implant components having posts orprojections oriented medially, with varying thicknesses, lengths, andcurvatures.

As shown in the figures, the upper surface of the tray component has a“keel type” structure in between the concave surfaces that areconfigured to mate with the femoral condyle surfaces of a femoralimplant. This “keel type” structure can be configured to slide within agroove in the femoral implant. The groove can comprise stoppingmechanisms at each end of the groove to keep the “keel type” structurewithin the track of the groove. This “keel type” structure and groovearrangement may be used in situations where a patient's posteriorcruciate ligament is removed as part of the surgical process and thereis a need to posteriorly stabilize the implant within the joint.

In certain embodiments, the tibial implant component can be designed andmanufactured to include the post or projection as a permanentlyintegrated feature of the implant component. However, in certainembodiments, the post or projection can be modular. For example, thepost or projection can be designed and/or manufactured separate from thetibial implant component and optionally joined with the component,either prior to (e.g., preoperatively) or during the implant procedure.For example, a modular post or projection and a tibial implant componentcan be mated using an integrating mechanism such as respective male andfemale screw threads, other male-type and female-type lockingmechanisms, or other mechanism capable of integrating the post orprojection into or onto the tibial implant component and providingstability to the post or projection during normal wear. A modular postor projection can be joined to a tibial implant component at the optionof the surgeon or practitioner, for example, by removing a plug or otherdevice that covers the integrating mechanism and attaching the modularpost or projection at the uncovered integrating mechanism.

The post or projection can include features that are patient-adapted(e.g., patient-specific or patient-engineered). In certain embodiments,the post or projection includes one or more features that are designedand/or selected preoperatively, based on patient-specific data includingimaging data, to substantially match one or more of the patient'sbiological features. For example, the length, width, height, and/orcurvature of one or more portions of the post or projection can bedesigned and/or selected to be patient-specific, for example, withrespect to the patient's intercondylar distance or depth, femoral shape,and/or condyle shape. Alternatively or in addition, one or more featuresof the post or projection can be engineered based on patient-specificdata to provide to the patient an optimized fit. For example, thelength, width, height, and/or curvature of one or more portions of thepost or projection can be designed and/or selected to bepatient-engineered. One or more thicknesses of the housing, receptacle,or bar can be matched to patient-specific measurements. One or moredimensions of the post or projection can be adapted based on one or moreimplant dimensions (e.g., one or more dimensions of the housing,receptacle or bar on the corresponding femoral implant component), whichcan be patient-specific, patient-engineered or standard. One or moredimensions of the post or projection can be adapted based on one or moreof patient weight, height, sex, and body mass index. In addition, one ormore features of the post or projection can be standard.

Optionally, referring to FIGS. 71A and 71B, an exemplary “keel type”structure or post can be adapted to the patient's anatomy. For example,the post can be shaped to enable a more normal, physiologic glide pathof the femur relative to the tibia. Thus, the post can deviate mediallyor lateral as it extends from its base to its tip. This medial orlateral deviation can be designed to achieve a near physiologic rollingand rotating action of the knee joint. The medial and lateral bending ofthe post can be adapted based on patient specific imaging data. Forexample, the mediolateral curve or bend of the post or keel can bepatient -derived or patient-matched (e.g., to match the physical orforce direction of PCL or ACL).

Alternatively or in addition, the post or keel can deviate at aparticular AP angle or bend, for example, the sagittal curve of the postor keel can be reflection of PCL location and orientation orcombinations of ACL and PCL location and orientation. The post canoptionally taper or can have different diameters and cross-sectionalprofiles, e.g. round, elliptical, ovoid, square, rectangular atdifferent heights from its base.

Different dimensions of the post or projection can be shaped, adapted,or selected based on different patient dimensions and implantdimensions. Examples of different technical implementations are providedin Table 14. These examples are in no way meant to be limiting. Someoneskilled in the art will recognize other means of shaping, adapting orselecting a tibial implant post or projection based on the patient'sgeometry including imaging data.

TABLE 14 Examples of different technical implementations of acruciate-sacrificing tibial implant component Corresponding patientanatomy, e.g., derived from imaging Post or projection feature studiesor intraoperative measurements Mediolateral width Maximum mediolateralwidth of patient intercondylar notch or fraction thereof Mediolateralwidth Average mediolateral width of intercondylar notch Mediolateralwidth Median mediolateral width of intercondylar notch Mediolateralwidth Mediolateral width of intercondylar notch in select regions, e.g.most inferior zone, most posterior zone, superior one third zone, midzone, etc. Superoinferior height Maximum superoinferior height ofpatient intercondylar notch or fraction thereof Superoinferior heightAverage superoinferior height of intercondylar notch Superoinferiorheight Median superoinferior height of intercondylar notchSuperoinferior height Superoinferior height of intercondylar notch inselect regions, e.g. most medial zone, most lateral zone, central zone,etc. Anteroposterior length Maximum anteroposterior length of patientintercondylar notch or fraction thereof Anteroposterior length Averageanteroposterior length of intercondylar notch Anteroposterior lengthMedian anteroposterior length of intercondylar notch Anteroposteriorlength Anteroposterior length of intercondylar notch in select regions,e.g. most anterior zone, most posterior zone, central zone, anterior onethird zone, posterior one third zone etc.

The height or M-L width or A-P length of the intercondylar notch can notonly influence the length but also the position or orientation of a postor projection from the tibial implant component.

The dimensions of the post or projection can be shaped, adapted, orselected not only based on different patient dimensions and implantdimensions, but also based on the intended implantation technique, forexample, the intended tibial component slope or rotation and/or theintended femoral component flexion or rotation. For example, at leastone of an anteroposterior length or superoinferior height can beadjusted if a tibial implant is intended to be implanted at a 7 degreesslope as compared to a 0 degrees slope, reflecting the relative changein patient or trochlear or intercondylar notch or femoral geometry whenthe tibial component is implanted. Moreover, at least one of ananteroposterior length or superoinferior height can be adjusted if thefemoral implant is intended to be implanted in flexion, for example, in7 degrees flexion as compared to 0 degrees flexion. The correspondingchange in post or projection dimension can be designed or selected toreflect the relative change in patient or trochlear or intercondylarnotch or femoral geometry when the femoral component is implanted inflexion.

In another example, the mediolateral width can be adjusted if one orboth of the tibial and/or femoral implant components are intended to beimplanted in internal or external rotation, reflecting, for example, aneffective elongation of the intercondylar dimensions when a rotatedimplantation approach is chosen. Features of the post or projection canbe oblique or curved to match corresponding features of the femoralcomponent housing, receptacle or bar. For example, the superior portionof the post projection can be curved, reflecting a curvature in the roofof the femoral component housing, receptacle, or bar, which itself mayreflect a curvature of the intercondylar roof. In another example, aside of a post or projection may be oblique to reflect an obliquity of aside wall of the housing or receptacle of the femoral component, whichitself may reflect an obliquity of one or more condylar walls.Accordingly, an obliquity or curvature of a post or projection can beadapted based on at least one of a patient dimension or a femoralimplant dimension. Alternatively, the post or projection of the tibialimplant component can be designed and/or selected based on generic orpatient-derived or patient-desired or implant-desired kinematics in one,two, three or more dimensions. Then, the corresponding surface(s) of thefemoral implant housing or receptacle can be designed and/or selected tomate with the tibial post or projection, e.g., in the ML plane.Alternatively, the post or projection of the femoral receptacle or boxor bar or housing can be designed and/or selected based on generic orpatient-derived or patient-desired or implant-desired kinematics in one,two, three or more dimensions. Then, the corresponding surface(s) of thepost or projection of the tibial implant can be designed and/or selectedto mate with the tibial post or projection, e.g., in the ML plane.

The tibial post or projection can be straight. Alternatively, the tibialpost or projection can have a curvature or obliquity in one, two orthree dimensions, which can optionally be, at least in part, reflectedin the internal shape of the box. One or more tibial projection or postdimensions can be matched to, designed to, adapted to, or selected basedon one or more patient dimensions or measurements. Any combination ofplanar and curved surfaces is possible.

In certain embodiments, the position and/or dimensions of the tibialimplant component post or projection can be adapted based onpatient-specific dimensions. For example, the post or projection can bematched with the position of the posterior cruciate ligament or the PCLinsertion. It can be placed at a predefined distance from anterior orposterior cruciate ligament or ligament insertion, from the medial orlateral tibial spines or other bony or cartilaginous landmarks or sites.By matching the position of the post with the patient's anatomy, it ispossible to achieve a better functional result, better replicating thepatient's original anatomy.

The tray component can be machined, molded, casted, manufactured throughadditive techniques such as laser sintering or electron beam melting orotherwise constructed out of a metal or metal alloy such as cobaltchromium. Similarly, the insert component may be machined, molded,manufactured through rapid prototyping or additive techniques orotherwise constructed out of a plastic polymer such as ultra highmolecular weight polyethylene. Other known materials, such as ceramicsincluding ceramic coating, may be used as well, for one or bothcomponents, or in combination with the metal, metal alloy and polymerdescribed above. It should be appreciated by those of skill in the artthat an implant may be constructed as one piece out of any of the above,or other, materials, or in multiple pieces out of a combination ofmaterials. For example, a tray component constructed of a polymer with atwo-piece insert component constructed one piece out of a metal alloyand the other piece constructed out of ceramic.

Each of the components may be constructed as a “standard” or “blank” invarious sizes or may be specifically formed for each patient based ontheir imaging data and anatomy. Computer modeling may be used and alibrary of virtual standards may be created for each of the components.A library of physical standards may also be amassed for each of thecomponents.

Imaging data including shape, geometry, e.g., M-L, A-P, and S-Idimensions, then can be used to select the standard component, e.g., afemoral component or a tibial component or a humeral component and aglenoid component that most closely approximates the select features ofthe patient's anatomy. Typically, these components will be selected sothat they are slightly larger than the patient's articular structurethat will be replaced in at least one or more dimensions. The standardcomponent is then adapted to the patient's unique anatomy, for exampleby removing overhanging material, e.g. using machining.

Thus, referring to the flow chart shown in FIG. 72A, in a first step,the imaging data will be analyzed, either manually or with computerassistance, to determine the patient specific parameters relevant forplacing the implant component. These parameters can include patientspecific articular dimensions and geometry and also information aboutligament location, size, and orientation, as well as potentialsoft-tissue impingement, and, optionally, kinematic information.

In a second step, one or more standard components, e.g., a femoralcomponent or a tibial component or tibial insert, are selected. Theseare selected so that they are at least slightly greater than one or moreof the derived patient specific articular dimensions and so that theycan be shaped to the patient specific articular dimensions.Alternatively, these are selected so that they will not interfere withany adjacent soft-tissue structures. Combinations of both are possible.

If an implant component is used that includes an insert, e.g., apolyethylene insert and a locking mechanism in a metal or ceramic base,the locking mechanism can be adapted to the patient's specific anatomyin at least one or more dimensions. The locking mechanism can also bepatient adapted in all dimensions. The location of locking features canbe patient adapted while the locking feature dimensions, for examplebetween a femoral component and a tibial component, can be fixed.Alternatively, the locking mechanism can be pre-fabricated; in thisembodiment, the location and dimensions of the locking mechanism willalso be considered in the selection of the pre-fabricated components, sothat any adaptations to the metal or ceramic backing relative to thepatient's articular anatomy do not compromise the locking mechanism.Thus, the components can be selected so that after adaptation to thepatient's unique anatomy a minimum material thickness of the metal orceramic backing will be maintained adjacent to the locking mechanism.

Since the tibia has the shape of a champagne glass, i.e., since ittapers distally from the knee joint space down, moving the tibial cutdistally will result in a smaller resultant cross-section of the cuttibial plateau, e.g., the ML and/or AP dimension of the cut tibia willbe smaller. For example, referring to FIG. 72B, increasing the slope ofthe cut will result in an elongation of the AP dimension of the cutsurface—requiring a resultant elongation of a patient matched tibialcomponent. Thus, in one embodiment it is possible to select an optimalstandard, pre-made tibial blank for a given resection height and/orslope. This selection can involve (1) patient-adapted metal with astandard poly insert; or (2) metal and poly insert, wherein both areadapted to patient anatomy. The metal can be selected so that based oncut tibial dimensions there is always a certain minimum metal perimeter(in one, two or three dimensions) guaranteed after patient adaptation sothat a lock mechanism will not fail. Optionally, one can determineminimal metal perimeter based on finite element modeling (FEA) (onceduring initial design of standard lock features, or patient specificevery time e.g. via patient specific FEA modeling).

The tibial tray can be selected (or a metal base for other joints) tooptimize percent cortical bone coverage at resection level. Thisselection can be (1) based on one dimension, e.g., ML; (2) based on twodimensions, e.g. ML and AP; and/or (3) based on three dimensions, e.g.,ML, AP, SI or slope.

The selection can be performed to achieve a target percentage coverageof the resected bone (e.g. area) or cortical edge or margin at theresection level (e.g. AP, ML, perimeter), e.g. 85%, 90%, 95%, 98% or100%. Optionally, a smoothing function can be applied to the derivedcontour of the patient's resected bone or the resultant selected,designed or adapted implant contour so that the implant does not extendinto all irregularities or crevaces of the virtually and then latersurgically cut bone perimeter.

Optionally, a function can be included for deriving the desired implantshape that allows changing the tibial implant perimeter if the implantoverhangs the cortical edge in a convex outer contour portion or in aconcave outer contour portion (e.g. “crevace”). These changes cansubsequently be included in the implant shape, e.g. by machining selectfeatures into the outer perimeter.

Those of skill in the art will appreciate that a combination of standardand customized components may be used in conjunction with each other.For example, a standard tray component may be used with an insertcomponent that has been individually constructed for a specific patientbased on the patient's anatomy and joint information.

Another embodiment incorporates a tray component with one half of atwo-piece insert component integrally formed with the tray component,leaving only one half of the two-piece insert to be inserted duringsurgery. For example, the tray component and medial side of the insertcomponent may be integrally formed, with the lateral side of the insertcomponent remaining to be inserted into the tray component duringsurgery. Of course, the reverse could also be used, wherein the lateralside of the insert component is integrally formed with the traycomponent leaving the medial side of the insert component for insertionduring surgery.

Each of these alternatives results in a tray component and an insertcomponent shaped so that once combined, they create a uniformly shapedimplant matching the geometries of the patient's specific joint.

The above embodiments are applicable to all joints of a body, e.g.,ankle, foot, elbow, hand, wrist, shoulder, hip, spine, or other joint.

For example, in a hip, an acetabular component can be designed orselected or adapted so that its peripheral margin will be closelymatched to the patient patient specific acetabular rim or perimeter.Optionally, reaming can be simulated for placement of an acetabular cupand the implant can then be designed or selected or adapted so that itwill be closely matched to the resultant acetabular rim after reaming.Thus, the exterior dimensions of the implant can be matched to thepatient's geometry in this fashion. Optionally, standard, rounddimensions of a polyethylene insert can be used with this embodiment.Similarly, a glenoid component can be matched to the glenoid rim,optionally after surgically preparing or resectioning all or portions ofthe glenoid rim. Thus, edge matching, designing, selecting or adaptingimplants including, optionally lock features, can be performed forimplants used in any joint of the body.

An implant component can include a fixed bearing design or a mobilebearing design. With a fixed bearing design, a platform of the implantcomponent is fixed and does not rotate. However, with a mobile bearingdesign, the platform of the implant component is designed to rotatee.g., in response to the dynamic forces and stresses on the joint duringmotion.

A rotating platform mobile bearing on the tibial implant componentallows the implant to adjust and accommodate in an additional dimensionduring joint motion. However, the additional degree of motion cancontribute to soft tissue impingement and dislocation. Mobile bearingsare described elsewhere, for example, in U.S. Patent ApplicationPublication No. 2007/0100462.

In certain embodiments, an implant can include a mobile-bearing implantthat includes one or more patient-specific features, one or morepatient-engineered features, and/or one or more standard features. Forexample, for a knee implant, the knee implant can include a femoralimplant component having a patient-specific femoral intercondylardistance; a tibial component having standard mobile bearing and apatient-engineered perimeter based on the dimensions of the perimeter ofthe patient's cut tibia and allowing for rotation without significantextension beyond the perimeter of the patient's cut tibia; and a tibialinsert or top surface that is patient-specific for at least thepatient's intercondylar distance between the tibial insert dishes toaccommodate the patient-specific femoral intercondylar distance of thefemoral implant.

As another example, in certain embodiments a knee implant can include afemoral implant component that is patient-specific with respect to aparticular patient's M-L dimension and standard with respect to thepatient's femoral intercondylar distance; a tibial component having astandard mobile bearing and a patient-engineered perimeter based on thedimensions of the perimeter of the patient's cut tibia and allowing forrotation without significant extension beyond the perimeter of thepatient's cut tibia; and a tibial insert or top surface that includes astandard intercondylar distance between the tibial insert dishes toaccommodate the standard femoral intercondylar distance of the femoralimplant.

7. Optimizing Soft-Tissue Tension, Ligament Tension, Balancing, Flexionand Extension Gap

The surgeon can, optionally, make adjustments of implant position and/ororientation such as rotation, bone cuts, cut height and selectedcomponent thickness, insert thickness or selected component shape orinsert shape. In this manner, an optimal compromise can be found, forexample, between biomechanical alignment and joint laxity orbiomechanical alignment and joint function, e.g., in a knee jointflexion gap and extension gap. Thus, multiple approaches exist foroptimizing soft-tissue tension, ligament tension, ligament balance,and/or flexion and extension gap. These include, for example, one ormore of the exemplary options described in Table 15.

TABLE 15 Exemplary approach options for optimizing soft-tissue tension,ligament tension, ligament balance, and/or flexion and extension gapOption # Description of Exemplary Option 1 Position of one or morefemoral bone cuts 2 Orientation of one or more femoral bone cuts 3Location of femoral component 4 Orientation of femoral component,including rotational alignment in axial, sagittal and coronal direction5 Position of one or more tibial bone cuts 6 Orientation of one or moretibial bone cuts including sagittal slope, mediolateral orientation 7Location of tibial component 8 Orientation of tibial component,including rotational alignment in axial, sagittal and coronal direction9 Tibial component height 10 Medial tibial insert or component orcomposite height 11 Lateral tibial insert or component or compositeheight 12 Tibial component profile, e.g., convexity, concavity, trough,radii of curvature 13 Medial tibial insert or component or compositeprofile, e.g. convexity, concavity, trough, radii of curvature 14Lateral tibial insert or component or composite profile, e.g. convexity,concavity, trough, radii of curvature 15 Select soft-tissue releases,e.g. partial or full releases of retinacula and/or ligaments,“pie-crusting” etc.

Any one option described in Table 15 can be optimized alone or incombination with one or more other options identified in the tableand/or known in the art for achieving different flexion and extension,abduction, or adduction, internal and external positions and differentkinematic requirements.

In one embodiment, the surgeon can initially optimize the femoral andtibial resections. Optimization can be performed by measuringsoft-tissue tension or ligament tension or balance for different flexionand extension angles or other joint positions before any bone has beenresected, once a first bone resection on a first articular surface hasbeen made and after a second bone resection on a first or secondarticular surface has been made, such as a femur and a tibia, humerusand a glenoid, femur and an acetabulum.

The position and orientation between a first implant component and asecond, opposing implant component or a first articular surface and atrial implant or a first trial implant and a second trial implant or analignment guide and an instrument guide and any combinations thereof canbe optimized with the use of, for example, interposed spacers, wedges,screws and other mechanical or electrical methods known in the art. Asurgeon may desire to influence joint laxity as well as joint alignment.This can be optimized for different flexion and extension, abduction, oradduction, internal and external rotation angles. For this purpose,spacers can be introduced at or between one or more steps in the implantprocedure. One or more of the spacers can be attached or in contact withone or more instruments, trials or, optionally, patient-specific molds.The surgeon can intraoperatively evaluate the laxity or tightness of ajoint using spacers with different thicknesses or one or more spacerswith the same thickness. For example, spacers can be applied in a kneejoint in the presence of one or more trials or instruments orpatient-specific molds and the flexion gap can be evaluated with theknee joint in flexion. The knee joint can then be extended and theextension gap can be evaluated. Ultimately, the surgeon selects for agiven joint an optimal combination of spacers and trial or instrument orpatient-specific mold. A surgical cut guide can be applied to the trialor instrument or patient-specific mold with the spacers optionallyinterposed between the trial or instrument or patient-specific mold andthe cut guide. In this manner, the exact position of the surgical cutscan be influenced and can be adjusted to achieve an optimal result.Someone skilled in the art will recognize other means for optimizing theposition of the surgical cuts. For example, expandable or ratchet-likedevices can be utilized that can be inserted into the joint or that canbe attached or that can touch the trial or instrument orpatient-specific mold. Hinge-like mechanisms are applicable. Similarly,jack-like mechanisms are useful. In principal, any mechanical orelectrical device useful for fine tuning the position of a cut guiderelative to a trial or instrument or patient-specific mold can be used.

A surgeon may desire to influence joint laxity as well as jointalignment. This can be optimized for different flexion and extension,abduction, or adduction, internal and external rotation angles. For thispurpose, for example, spacers can be introduced that are attached orthat are in contact with one or more trials or instruments orpatient-specific molds. The surgeon can intraoperatively evaluate thelaxity or tightness of a joint using spacers with different thickness orone or more spacers with the same thickness. For example, spacers can beapplied in a knee joint in the presence of one or more instruments ortrials or molds and the flexion gap can be evaluated with the knee jointin flexion. Different thickness trials can be used. The terms spacer orinsert can be used interchangeably with the term trial.

In certain embodiments, the surgeon can elect to insert different trialsor spacers or instruments of different thicknesses in the medial and/orlateral joint space in a knee. This can be done before any bone has beenresected, once a first bone resection on a first articular surface hasbeen made and after a second bone resection on a first or secondarticular surface has been made, such as a femur and a tibia or a medialand a lateral condyle or a medial and a lateral tibia. The joint can betested for soft-tissue tension, ligament tension, ligament balanceand/or flexion or extension gap for different orientations or kinematicrequirements using different medial and lateral trial or spacerthicknesses, e.g., at different flexion and extension angles. Surgicalbone cuts can subsequently optionally be adapted or changed.Alternatively, different medial and lateral insert thickness or profilesor composite heights can be selected for the tibial component(s). Forexample, combinations of medial and lateral spacers or trials havingthicknesses described in Table 16 can be inserted.

TABLE 16 Exemplary medial and lateral spacer, trial, and/or insertheights that can be used in combination Medial spacer, Lateral spacer,trial, and/or trial, and/or insert height insert height Note 6 mm 6 mmSame medial and lateral spacer, trial, and/or insert 7 mm 7 mm height 8mm 8 mm 9 mm 9 mm 10 mm 10 mm 11 mm 11 mm 12 mm 12 mm 13 mm 13 mm 14 mm14 mm 15 mm 15 mm 16 mm 16 mm 6 mm 7 mm Different medial and lateralspacer, trial, and/or insert 6 mm 8 mm (6 mm medial spacer, trial,and/or insert height with 6 mm 9 mm various lateral spacer, trial,and/or insert heights) 6 mm 10 mm 6 mm 11 mm 6 mm 12 mm 6 mm 13 mm 6 mm14 mm 6 mm 15 mm 6 mm 16 mm 7 mm 6 mm Different medial and lateralspacer, trial, and/or insert 7 mm 8 mm height (7 mm medial spacer,trial, and/or insert 7 mm 9 mm height with various lateral spacer,trial, and/or insert 7 mm 10 mm heights) 7 mm 11 mm 7 mm 12 mm 7 mm 13mm 7 mm 14 mm 7 mm 15 mm 7 mm 16 mm 8 mm 6 mm Different medial andlateral spacer, trial, and/or insert 8 mm 7 mm height (8 mm medialspacer, trial, and/or insert 8 mm 9 mm height with various lateralspacer, trial, and/or insert 8 mm 10 mm heights) 8 mm 11 mm 8 mm 12 mm 8mm 13 mm 8 mm 14 mm 8 mm 15 mm 8 mm 16 mm 9 mm 6 mm Different medial andlateral spacer, trial, and/or insert 9 mm 7 mm height (9 mm medialspacer, trial, and/or insert 9 mm 8 mm height with various lateralspacer, trial, and/or insert 9 mm 10 mm heights) 9 mm 11 mm 9 mm 12 mm 9mm 13 mm 9 mm 14 mm 9 mm 15 mm 9 mm 16 mm 10 mm 6 mm Different medialand lateral spacer, trial, and/or insert 10 mm 7 mm height (10 mm medialspacer, trial, and/or insert 10 mm 8 mm height with various lateralspacer, trial, and/or insert 10 mm 9 mm heights) 10 mm 11 mm 10 mm 12 mm10 mm 13 mm 10 mm 14 mm 10 mm 15 mm 10 mm 16 mm 11 mm 6 mm Differentmedial and lateral spacer, trial, and/or insert 11 mm 7 mm height (11 mmmedial spacer, trial, and/or insert 11 mm 8 mm height with variouslateral spacer, trial, and/or insert 11 mm 9 mm heights) 11 mm 10 mm 11mm 12 mm 11 mm 13 mm 11 mm 14 mm 11 mm 15 mm 11 mm 16 mm 12 mm 6 mmDifferent medial and lateral spacer, trial, and/or insert 12 mm 7 mmheight (12 mm medial spacer, trial, and/or insert 12 mm 8 mm height withvarious lateral spacer, trial, and/or insert 12 mm 9 mm heights) 12 mm10 mm 12 mm 11 mm 12 mm 13 mm 12 mm 14 mm 12 mm 15 mm 12 mm 16 mm 13 mm6 mm Different medial and lateral spacer, trial, and/or insert 13 mm 7mm height (13 mm medial spacer, trial, and/or insert 13 mm 8 mm heightwith various lateral spacer, trial, and/or insert 13 mm 9 mm heights) 13mm 10 mm 13 mm 11 mm 13 mm 12 mm 13 mm 14 mm 13 mm 15 mm 13 mm 16 mm 14mm 6 mm Different medial and lateral spacer, trial, and/or insert 14 mm7 mm height (14 mm medial spacer, trial, and/or insert 14 mm 8 mm heightwith various lateral spacer, trial, and/or insert 14 mm 9 mm heights) 14mm 10 mm 14 mm 11 mm 14 mm 12 mm 14 mm 13 mm 14 mm 15 mm 14 mm 16 mm 15mm 6 mm Different medial and lateral spacer, trial, and/or insert 15 mm7 mm height (15 mm medial spacer, trial, and/or insert 15 mm 8 mm heightwith various lateral spacer, trial, and/or insert 15 mm 9 mm heights) 15mm 10 mm 15 mm 11 mm 15 mm 12 mm 15 mm 13 mm 15 mm 14 mm 15 mm 16 mm 16mm 6 mm Different medial and lateral spacer, trial, and/or insert 16 mm7 mm height (16 mm medial spacer, trial, and/or insert 16 mm 8 mm heightwith various lateral spacer, trial, and/or insert 16 mm 9 mm heights) 16mm 10 mm 16 mm 11 mm 16 mm 12 mm 16 mm 13 mm 16 mm 14 mm 16 mm 15 mm

Thus, by using separate medial and/or lateral spacers or trials orinserts, it is possible to determine an optimized combination of medialor lateral tibial components, for example with regard to medial andlateral composite thickness, insert thickness or medial and lateralimplant or insert profile. Thus, medial and/or lateral tibial implant orcomponent or insert thickness can be optimized for a desired soft-tissueor ligament tension or ligament balance for different flexion andextension angles and other joint poses. This offers a unique benefitbeyond traditional balancing using bone cuts and soft-tissue releases.In one embodiment, the surgeon can place the tibial and femoral surgicalbone cuts and perform the proper soft-tissue or ligament tensioning orbalancing entirely via selection of a medial or lateral tibial insert orcomposite thickness and/or profile. Additional adaptation andoptimization of bone cuts and soft-tissue releases is possible.

FIGS. 73A through 75C show various exemplary spacers or trials orinserts for adjusting and optimizing alignment, tension, balance, andposition (e.g., as described in Table 15 above) during a knee implantsurgery. In particular, FIG. 73A depicts a medial balancer chip insertfrom top view to show the superior surface of the chip. FIG. 73B depictsa side view of a set of four medial balancer chip inserts thatincrementally increase in thickness by 1 mm. A corresponding set oflateral balancing chip inserts (having a range of thicknesses) can beused in conjunction with a set of medial balancing chip inserts. In thisway, the joint can be optimized using independent medial and lateralbalancing chips inserts having different thicknesses. As indicated withthe first chip in the figure, the superior surface 7302 of a balancingchip insert engages the femur and the inferior surface 7304 engages thetibia. In certain embodiments, one or both of the superior surface 7302and/or the inferior surface 7304 can be patient-adapted to fit theparticular patient. In certain embodiments, a balancing chip can includea resection surface to guide a subsequent surgical bone cut.

FIG. 73C depicts a medial balancing chip being inserted in flexionbetween the femur and tibia. FIG. 73D depicts the medial balancing chipinsert in place while the knee is brought into extension. Optionally, alateral balancing chip also can be placed between the lateral portionsof the femur and tibia. Medial and lateral balancing chips havingdifferent thicknesses can be placed as shown in FIGS. 73C and 73D, untila desired tension is observed medially and laterally throughout thepatient's range of motion. As shown in FIG. 73E, in certain embodiments,a cutting guide can be attached to the medial balancing chip insert, tothe lateral balancing chip insert, or to both, so that the resectioncuts are made based on the selected medial and lateral balancing chipinserts. Optionally, one or more surfaces of one or both balancing chipsalso can act as a cutting guide. As shown in FIG. 73F, the inferiorsurface of the medial balancing chip can act as cutting guide surfacefor resectioning the medial portion of the tibia.

FIG. 74A depicts a set of three medial spacer block inserts havingincrementally increasing thicknesses, for example, thicknesses thatincrease by 1 mm, by 1.5 mm, or by 2 mm. A corresponding set of lateralmedial spacer block inserts (having a range of thicknesses) can be usedin conjunction with a set of medial spacer block inserts. A spacer blockinsert can be used, for example, to provide the thickness of a tibialimplant component (optionally with or without the additional thicknessof a tibial implant component insert) during subsequent implantationsteps and prior to placement of the tibial implant component. In certainembodiments, the spacer block insert can include a portion for attachinga trial a tibial implant component insert, so that the precisethicknesses of different combinations of tibial implant components andcomponent inserts can be assessed. By using medial and lateral spacerblock inserts of different thicknesses, the balancing, tensioning,alignment, and/or positioning of the joint can continue to be optimizedthroughout the implantation procedure. In certain embodiments, one ormore features of a spacer block insert can be patient-adapted to fit theparticular patient. In certain embodiments, a spacer block insert caninclude a feature for attaching or stabilizing a cutting guide and/or afeature for guiding a cutting tool.

FIG. 74B depicts a set of two medial femoral trials having incrementallyincreasing thicknesses, for example, thicknesses that increase by 1 mm,by 1.5 mm, or by 2 mm. A corresponding set of lateral femoral trials(having a range of thicknesses) can be used in conjunction with the setof medial femoral trials. A femoral trial can be used, for example, totest variable thicknesses and/or features of a femoral implant componentduring implantation steps prior to placement of the tibial implantcomponent. By using medial and lateral femoral trials of differentthicknesses, the balancing, tensioning, alignment, and/or positioning ofthe joint can continue to be optimized throughout the implantationprocedure. In certain embodiments, one or more features of a femoraltrial can be patient-adapted to fit the particular patient. In certainembodiments, a femoral trial can include a feature for attaching orstabilizing a cutting guide and/or a feature for guiding a cutting tool.

FIG. 74C depicts a medial femoral trial in place and a spacer blockbeing inserted to evaluate the balance of the knee in flexion andextension. Spacer blocks having different thicknesses can be insertedand evaluated until an optimized thickness is identified. Optionally, alateral femoral trial also can be placed between the lateral portions ofthe femur and tibia and a lateral spacer block inserted and evaluatedalong with the medial spacer block. Medial and lateral spacer blockshaving different thicknesses can be placed and removed until a desiredtension is observed medially and laterally throughout the patient'srange of motion. Then, a tibial implant component and/or tibial implantcomponent insert can be selected to have a thickness based on thethickness identified by evaluation using the femoral trial and spacerblock. In this way, the selected medial a tibial implant component(and/or tibial implant component insert) and the lateral tibial implantcomponent (and/or tibial implant component insert) can have differentthicknesses.

FIG. 75A depicts a set of three medial tibial component insert trialshaving incrementally increasing thicknesses, for example, thicknessesthat increase by 0.5 mm, by 1 mm, by 1.5 mm, or by 2 mm. A correspondingset of lateral tibial component insert trials (having a range ofthicknesses) can be used in conjunction with the set of medial tibialcomponent insert trials. A tibial component insert trial can be used,for example, to determine the best insert thickness and/or features of atibial component insert during the final implantation steps. By usingmedial and lateral tibial component insert trials of differentthicknesses and/or configurations, the balancing, tensioning, alignment,and/or positioning of the joint can be optimized even in the final stepsof the procedure. In certain embodiments, one or more features of atibial component insert trial can be patient-adapted to fit theparticular patient. FIG. 75B depicts the process of placing and addingvarious tibial component insert trials and FIG. 75C depicts the processof placing the selected tibial component insert.

The sets of exemplary spacers, trials, and inserts described inconnection with FIGS. 73A through 75C can be expanded to includespacers, trials, and/or inserts having various intermediate thicknesses(e.g., in increments of 0.5 mm, 0.25 mm, and/or 0.1 mm) and/or havingvarious other selection features. For example, sets of femoral and/ortibial insert trials can include different bone-facing and/orjoint-facing surfaces from which the surgeon can select the optimumavailable surface for further steps in the procedure.

Using the various spacers, trials, and inserts described above, the kneejoint can be flexed and the flexion gap can be evaluated. In addition,the knee can be extended and the extension gap can be evaluated.Ultimately, the surgeon will select an optimal combination of spacers ortrials for a given joint, instrument, trial or mold. A surgical cutguide can be applied to the trial, instrument, or mold with the spacersoptionally interposed between the trial, instrument or mold and the cutguide. In this manner, the exact position of the surgical cuts can beinfluenced and can be adjusted to achieve an optimal result. Someoneskilled in the art will recognize other means for optimizing theposition of the surgical cuts. For example, expandable or ratchet-likedevices can be utilized that can be inserted into the joint or that canbe attached or that can touch the trial, instrument or mold. Hinge-likemechanisms are applicable. Similarly, jack-like mechanisms are useful.In principal, any mechanical or electrical device useful for fine tuningthe position of the cut guide relative to the trial or instrument ormolds can be used. The trials or instruments or molds and any relatedinstrumentation such as spacers or ratchets can be combined with atensiometer to provide a better intraoperative assessment of the joint.The tensiometer can be utilized to further optimize the anatomicalignment and tightness or laxity of the joint and to improvepost-operative function and outcomes. Optionally local contact pressuresmay be evaluated intraoperatively, for example using a sensor like theones manufactured by Tekscan, South Boston, Mass.

8. Guide Tools for Installing a Joint Implant

A variety of traditional guide tools are available to assist surgeons inpreparing a joint for an implant, for example, for resectioning one ormore of a patient's biological structures during a joint implantprocedure. However, these traditional guide tools typically are notdesigned to match the shape (contour) of a particular patient'sbiological structure(s). Moreover, these traditional guide toolstypically are not designed to impart patient-optimized placement for theresection cuts. Thus, using and properly aligning traditional guidetools, as well as properly aligning a patient's limb (e.g., inrotational alignment, in varus or valgus alignment, or alignment inanother dimension) in order to orient these traditional guide tools, canbe an imprecise and complicated part of the implant procedure.

Certain embodiments described herein provide improved surgical guidetools and methods for preparing a patient's biological structure duringa joint implant procedure.

8.1 Patient-Specific Guide Tools

Certain embodiments include a guide tool having at least onepatient-specific bone-facing surface portion that substantiallynegatively-matches at least a portion of a biological surface at thepatient's joint. The guide tool further can include at least oneaperture for directing movement of a surgical instrument, for example, asecuring pin or a cutting tool. One or more of the apertures can bedesigned to guide the surgical instrument to deliver a patient-optimizedplacement for, for example, a securing pin or resection cut. In additionor alternatively, one or more of the apertures can be designed to guidethe surgical instrument to deliver a standard placement for, forexample, a securing pin or resection cut. As used herein, “jig” also canrefer to guide tools, for example, to guide tools that guideresectioning of a patient's biological structure. Alternatively, certainguide tools can be used for purposes other than guiding a drill orcutting tool. For example, balancing and trial guide tools can be usedto assess knee alignment and/or fit of one or more implant components orinserts.

Certain embodiments can include a guide tool that includes at least onepatient-specific bone-facing surface that substantiallynegatively-matches at least a portion of a biological surface at thepatient's joint. The patient's biological surface can include cartilage,bone, tendon, and/or other biological surface. For example, in certainembodiments, patient-specific data such as imaging data of a patient'sjoint can be used to select and/or design an area on the articularsurface that is free of articular cartilage. The area can be free ofarticular cartilage because it was never cartilage covered or becausethe overlying cartilage has been worn away. The imaging test can bespecifically used to identify areas of full or near full thicknesscartilage loss for designing the contact surface on the bone-facingsurface of a patient-specific guide tool. Alternatively, the area can befree of articular cartilage because an osteophyte has formed and isextending outside the cartilage. The guide tool then can rest directlyon the bone, e.g., subchondral bone, marrow bone, endosteal bone or anosteophyte. By selecting and/or designing an area of the articularsurface that is free of articular cartilage, it is possible to (a)reference the guide tool against the articular surface and (b) referenceit against bone rather than cartilage.

In certain embodiments, patient-specific data such as imaging test dataof a patient's joint can be used to identify a contact area on thearticular surface for deriving an area on the bone-facing surface of aguide tool to substantially negatively-match the contact area on thesubchondral bone surface. While the area may be covered by articularcartilage, the guide tool surface area can be specifically designed tomatch the subchondral bone contact area. The guide tool can have one ormultiple areas that substantially negatively-match one or multiplecontact areas on the subchondral bone surface. Intraoperatively, thesurgeon can elect to place the guide tool on the residual cartilage.Optionally, the surgeon then can mark the approximate contact area onthe cartilage and remove the overlying cartilage in the marked areabefore replacing the guide tool directly onto the subchondral bone. Inthis manner, the surgeon can achieve more accurate placement of theguide tools that substantially negatively-matches subchondral bone.

In certain embodiments, patient-specific data such as imaging test dataof a patient's joint can be used to identify a contact area on thearticular surface for deriving an area on the bone-facing surface of aguide tool that substantially negatively-matches the endosteal bone orbone marrow contact area. While the area may be covered by articularcartilage, the guide tool surface area can be specifically designed tomatch the endosteal bone or bone marrow. The guide tool can have one ormultiple areas that substantially negatively-match one or multiple areason the endosteal bone or bone marrow. Intraoperatively, the surgeon canelect to place the guide tool on the residual cartilage. Optionally, thesurgeon then can mark the approximate contact area on the cartilage andsubsequently remove the overlying cartilage in the marked area beforereplacing the guide tool directly onto the endosteal bone or bonemarrow. In this manner, the surgeon can achieve more accurate placementof guide tools that match endosteal bone or bone marrow.

In certain embodiment, the articular surface or the margins of thearticular surface can include one or more osteophytes. The guide toolcan rest on the articular surface, e.g., on at least one of normalcartilage, diseased cartilage or subchondral bone, and it can includethe shape of the osteophyte. In certain embodiments, patient-specificdata such as imaging test data of a patient's joint can be used toderive an area on the bone-facing surface of the guide tool thatsubstantially negatively-matches the patient's articular surfaceincluding the osteophyte. In this manner, the osteophyte can provideadditional anatomic referencing for placing the guide tool. In certainembodiments, the osteophyte can be virtually removed from the joint onthe 2D or 3D images and the contact surface of the guide tool can bederived based on the corrected surface without the osteophyte. In thissetting, the surgeon can remove the osteophyte intraoperatively prior toplacing the guide tool.

Certain embodiments can include a guide tool that is flexible. The guidetool's flexibility, optionally in combination with a patient-specificbone-facing surface, can allow it to snap-fit into position onto thepatient's biological structure. For example, the guide tool can besnap-fit to a patient's biological structure by applying force to theguide tool to cause it to expand and engage the structure. During orfollowing the expansion and engagement, the tool can be adjusted so thatthe bone-facing surface engages the corresponding surface of thebiological structure.

The flexibility of the guide tool can be altered or enhanced usingmaterials and processes known in the art. For example, various typesand/or combinations of polymers and polymer manufacturing techniques canbe used to make a guide tool with the appropriate flexibility to providea snap-fit.

The bone-facing surface of the guide tool can be patient-specific (e.g.,substantially negatively-match) for one or more surface dimensions orfeatures of the patient's biological surface including, for example,width, area, height, distance, angle, and curvature. For example, incertain embodiments, a dimension or feature of the patient's biologicalstructure can be assessed to include the cartilage on its surface. Incertain other embodiments, a dimension or feature can be assessed basedon the patient's bone surface, for example, subchondral bone surface.

If a subchondral bone surface is used to assess the patient's biologicalsurface, a standard cartilage thickness (e.g., 2 mm), or an approximatecartilage thickness derived from patient-specific data (e.g., age,joint-size, contralateral joint measurements, etc.) can be used as partof the design for the guide tool, for example, to design the size andbone-facing surface of the guide tool. The standard or approximatecartilage thickness can vary in thickness across the assessed surfacearea. In certain embodiments, this design can be used with a similarlydesigned implant, for example, an implant designed to include a standardor approximate cartilage thickness.

8.2 Patient-Engineered Guide Tools

In certain embodiments, a guide tool includes at least one feature fordirecting a surgical instrument to deliver a patient-engineered featureto the patient's biological structure, for example, a resected hole or aresection cut for engaging a patient-engineered implant peg or apatient-engineered implant bone-facing surface. In addition to thepatient-engineered feature, in certain embodiments one or more of theguide tool's bone-facing surfaces can be designed to be patient-specificso that it substantially negatively-matches a portion of the patient'sjoint surface. In addition or alternatively, one or more of the guidetool's bone-facing surfaces can be standard in shape.

Example 14 below describes a set of patient-optimized guide tools thatcan be used to perform patient-optimized resection cuts to the femur inpreparation for implanting a femoral knee implant component havingpatient-optimized bone cuts. As described in Example 14, one or moreguide tools can be used to prepare a joint for a patient-engineeredimplant.

8.3 Exemplary Guide Tool Configurations

The guide tools described herein can include any combination ofpatient-specific features, patient-engineered features, and/or standardfeatures. For example, a patient-specific guide tool includes at leastone feature that is preoperatively designed and/or selected tosubstantially match one or more of the patient's biological features. Apatient-engineered guide tool includes at least one feature that isdesigned or selected based on patient-specific data to optimize one ormore of the patient's biological features to meet one or moreparameters, for example, as described elsewhere here, such as in Section4. A standard guide tool includes at least one feature that is selectedfrom among a family of limited options, for example, selected from amonga family of 5, 6, 7, 8, 9, or 10 options. Accordingly, any one guidetool can be both patient-specific in view of its patient-specificfeatures and patient-engineered in view of its patient-engineeredfeatures. Such a guide tool also can include standard features as well.Table 17 describes the various combinations of three features of asingle guide tool with regard to being patient-specific features,patient-engineered features, and/or standard features of the exemplaryguide tools. Moreover, in certain embodiments a set or kit of guidetools is provided in which certain guide tools in the set or kit includepatient-specific, patient-engineered, and/or standard features. Forexample, a set or kit of guide tools can include any two or more guidetools described in Table 17.

TABLE 17 Patient-specific, patient-engineered, and standard features ofexemplary guide tools Feature Feature Feature Exemplary Guide tool #1 #2#3 A guide tool that includes at least 3 PS P P P features A guide toolthat includes at least 3 PE PE PE PE features A guide tool that includesat least 3 S St St St features A guide tool that includes at least 2 PSP P PE features and at least 1 PE feature P PE P PE P P A guide toolthat includes at least 2 PS P P St features and at least 1 S feature PSt P St P P A guide tool that includes at least 1PS PE PE P feature andat least 2 PE features PE P PE P PE PE A guide tool that includes atleast 1PS St St P feature and at least 2 S feature St P St P St St Aguide tool that includes at least 2PE PE PE St features and at least 1 Sfeature PE St PE St PE PE A guide tool that includes at least 1PE St StPE feature and at least 2 S features St PE St PE St St A guide tool thatincludes at least 1PS P PE St feature. at least 1 PE feature, and atleast 1 S P St PE feature PE P St PE St P St P PE St PE P P indicates apatient-specific feature, PE indicates a patient-engineered feature, andSt indicates a standard feature

A guide tool can be used for one or more purposes during an implantprocedure. For example, one or more guide tools can be used to establishresected holes in a patient's biological structure, to establishresected cuts in a patient's biological structure, and/or to balance orestimate fit of a joint implant. The following subsections describeexemplary guide tools and guide tool features that can help to establishresected holes, to establish resected cuts, and to balance or estimatefit of a joint implant.

As shown in FIG. 76, a guide tool 7600 can include one or more apertures7602 for establishing resected holes in a patient's biologicalstructure. One or more of these resected holes can be used to engage apeg, which can be used to secure one or more subsequently used guidetools, e.g., guide tools for establishing resection cuts, into properposition on the biological surface. For example, a subsequently usedguide tool can include one or more attached pegs that correspond to theone or more holes resected using, for example, using the guide tool ofFIG. 76. In particular, the subsequently used guide tool can be securedonto the biological surface by sliding the pegs into the appropriateresected holes. Alternatively, an independent peg can be placed into theresected hole and, then, a subsequently used guide tool having aperturescorresponding to the independent pegs can be secured onto the biologicalsurface by sliding the apertures over the independent pegs. In certainembodiments, the exemplary guide tool shown in FIG. 76 can includeanterior and posterior portions that are extended and the material ispliable so that the guide tool can snap-fit onto the femur.

In certain embodiments, one or more attached pegs (i.e., attached to aguide tool) can be detachable, so that, once detached, they can be usedto secure a subsequent guide tool or implant component having acorresponding aperture. In certain embodiments, a first guide tool canbe secured to the biological structure and a second guide can be securedto the first guide tool. For example, an attached or independent peg canextend from the resected hole, through the aperture of the first guidetool and into a corresponding aperture of the second guide tool.Alternatively or in addition, the second guide tool can include afeature that engages an aspect of the aperture on the first implant. Forexample, a portion of the aperture on the second guide tool can be widerthan the aperture on the first guide tool and engage a raised aperturecollar surrounding the aperture on the first guide tool. Alternatively,the second aperture can include a sleeve that slide into the aperture onthe first guide tool.

Alternatively or in addition, one or more of these resected holes can beused to secure an implant component. For example, one or more pegsprojecting from the bone-facing surface of the implant component can beplaced into the resected hole to fix the placement of the implantcomponent. In certain embodiments, cement can be applied to the resectedhole and/or the implant component peg to secure the placement of theimplant.

A variety of aperture configurations can be used for the guide toolsdescribed herein. In certain embodiments, a guide tool apertureconfiguration can be patient-engineered to engage a particularpatient-engineered peg configuration on the corresponding implantcomponent. Moreover, aperture features such as size, shape, angle, andoptionally, stop depth, can be designed to substantially match the pegfeatures for the corresponding implant component. For example, incertain embodiments the aperture cross-section can be round to match around peg on the implant component. However, in certain embodiments, assuggested by FIG. 53B, the aperture cross-section can include a “+” orcross-like configuration to match the corresponding peg on the implantcomponent.

A variety of aperture sizes can be used. For example, a 7 mm diameteraperture can be used. Moreover, the aperture can be oriented toestablish a resected hole at any angle. For example, an aperture can beoriented to establish a resected hole in line with the femoralmechanical axis. Alternatively, an aperture can be oriented to establisha resected hole at an anterior-leaning angle to match the angle of thecorresponding implant peg. For example, one or more apertures can beoriented anteriorly to establish a 5 degree, 5-10 degree, 10 degree,10-15 degree, and/or 15 degree anterior-leaning angle relative to thefemoral mechanism axis. The aperture can be oriented to establish aresected hole that is oriented at the same angle or at different anglesas one or both of the anterior and posterior cuts of the implantcomponent. In certain embodiments, a depth-stop can be used so that theaperture allows a resected hole having a certain maximum depth.

In certain embodiments, a guide tool includes at least one moveableaperture and, optionally, a moveable corresponding bushing. FIG. 77depicts a guide tool having a moveable lateral aperture and bushing.Specifically, the lateral aperture and bushing in the figure aremoveable in the A-P direction. However, a moveable aperture (and,optionally, a moveable bushing) can be moveable in the A-P direction, inthe M-L direction, or in all directions from the aperture center (e.g.,can be rotated in a circular pattern). Moreover, the guide tool caninclude two or more moveable apertures. For example, a lateral apertureand a medial aperture, and optionally one or both correspondingbushings, can be moveable. Alternatively, one or more apertures (andoptional bushings) can be fixed, for example, as is the medial apertureand bushing in FIG. 77.

The guide tool that includes one or more moveable apertures also caninclude one or more patient-specific features, one or morepatient-optimized features, and/or one or more standard features.Moreover, the guide tool can be used with a subsequently used guide toolor implant that includes one or more patient-specific features, one ormore patient-optimized features, and/or one or more standard features.

A guide tool that includes one or more moveable apertures forestablishing resected holes can be used during surgery to adjust theorientation of subsequently placed guide tools and/or implantcomponents. For example, one or more moveable apertures in a femoralguide tool can be used to adjust the femoral flexion, femoral rotation,and/or tibial external rotation of the particular patient's femoralimplant.

With reference to the exemplary guide tool shown in FIG. 77, a surgeoncan snap-fit the guide tool on the femur, observe placement of themoveable aperture as well as other guide tool features relative to oneor more biological landmarks, and, if appropriate, move the moveableaperture in order to adjust the orientation of the subsequentlyinstalled femoral implant component on the femur. For example, if thesurgeon moves the lateral aperture posteriorly to the 3 degree mark, asshown in the figure, the lateral resected hole and engaging lateral pegof the subsequently installed femoral implant component also would beshifted posteriorly. With the medial aperture fixed, this wouldposteriorly flex the lateral side of the implant component and axiallyrotate the orientation of the implant component on the femur. As shownin FIG. 77, the movable bushing can be limited to one or more ranges ofmotion and can be accompanied by markings and/or values displayed on thetool surface indicating the rotation in relation to one or more axes.Moreover, in certain embodiments, patient-specific information and/orstandard rules can be used to limit the extent of movement of themoveable aperture. For example, the limit of posterior movement of theaperture in the guide tool can be established as the point that allows asubsequent guide tool to guide a lateral posterior bone resection thatremoves some minimum amount of bone, for example, so that the intersectbetween the posterior resection cut and posterior chamfer cut is belowthe bone surface.

In certain embodiments, the movable aperture also could allow for abalancing technique. For example, a navigation chip can be placed intothe lateral joint in flexion, e.g., as a laminar spreader. This rotatesthe femur internally and the joint gap can be balanced by moving thelateral aperture, for example, posteriorly. So we have all fourtechniques integrated into our system and everyone's believe would besatisfied. The surgeon could then decide what he wants right there atsurgery.

In certain embodiments, the extent limit of movement of the moveableaperture in the A-P direction can be limited to 3 degrees, less than 3degrees, 5 degrees, less than 5 degrees, 7 degrees, and/or less than 7degrees.

In certain embodiments, instead of including a moveable aperture, theguide tool can include one or more alternative apertures and/or anextended opening, for example, and opening that includes the approximatearea through which a moveable aperture can move. Then, a bushing (e.g.,metal or plastic) or other device can snap, slide, or lock into placeonto one of the alternative apertures or at a certain location in theextended opening. For example, the bushing or other device could lockinto place at alternative apertures or in the extended opening at 3, 5and 7 degrees. In this way, the surgeon can alter the implantorientation as he or she deems appropriate. Alternatively, a guide toolcan include an aperture bushing that is fixed in one location but canswivel (e.g., tilt). For example, in certain embodiments, a bushing canswivel or tilt in one direction, in two directions, or all directionsabout a fixed point. The amount of swivel or tilt can be, for example,between 0 and 7 degrees, up to 7 degrees, between 1 and 7 degrees,and/or between 3 and 7 degrees in one or more directions.

The guide tools described herein can include features and apertures forvarious steps in a joint replacement procedure. For example, in certainembodiments, one or more guide tools can be used to establish all theresection cuts associated with installation of a particular implantcomponent. As noted above, one or more of the guide tools can includeone more patient-specific features and/or one or more patient-engineeredfeatures and/or one or more standard features.

In certain embodiments, a set of three guide tools can be used toestablish all the resection cuts associated with installation of aparticular implant component. For example, the three guide tools shownin FIG. 76 or 77, FIG. 78, and FIGS. 79A and 79B can be used together toestablish all the resection cuts associated with installation of afemoral implant component. In particular, FIGS. 76 and 77 each shows apeg hole driver guide tool for establishing pin or peg holes forsubsequent guide tools and, optionally, for the femoral implantcomponent. This tool can be used to establish the direction of pegs usedby subsequent tools and/or the implant component and can be specificallymatched to the patient just like the implant component. Subsequentlyplaced guide tools can be placed with respect to these peg hole featuresto ensure that the bone preparation is performed per the intendedimplant design. FIG. 78 shows a guide tool for making distal andposterior resection cuts to the distal femur and FIGS. 79A and 79B showtwo options for a third guide tool for making anterior and posteriorchamfer cuts. The particular set of guide tools shown in these figuresis designed for a tibia first technique; however, the features of theguide tools for preparing a knee joint as described herein can beapplied to both a tibia first technique and to a femur first technique.

Furthermore, a spacer, such as a lateral spacer, can be used forbalancing to equal distal asymmetry. The spacer can includepatient-specific and/or patient-engineered features. A series ofbalancer chips with thicknesses can be included, for example a series ofchips having 1 mm increases in thickness. Alternatively or in addition,a guide tool can include an integrated spacer thickness to allow surgeonto assess tension without needing a spacer. For example, a guide toolfor establishing femoral resection cuts can include an integrated spacehaving a tibial resection depth added to the guide tool externalsurface.

One or more guide tools can be selected and/or designed to includepatient-specific and/or patient-engineered features. For example, thepeg hole driver guide tool shown in FIG. 76 can include, at least inpart, a patient-specific bone-facing surface that substantially matchesa particular patient's femoral surface. Moreover, such guide tools caninclude flexible material, such as nylon plastic, to allow the tool tosnap-fit onto the particular patient's femur, as suggested by the peghole driver guide tool shown in FIG. 76. Other features, such as peghole angle, peg hole placement, peg hole size, tool thickness,joint-facing surface, and other features can be patient-specific orpatient-engineered. Alternatively or in addition, one or more featurescan be standard. For example, for the peg hole driver guide tool shownin FIG. 76, the peg size is 6 mm, which can accommodate a quarter-inchdrill size; however, any peg hole size can be used.

Resection cut guide tools can be designed to be patient-specific ontheir bone-facing surface to allow a snap-fit onto a particularpatient's femur. Moreover, other features, such as thickness,joint-facing surface, and peg placement and size, also can bepatient-specific or patient-engineered. Alternatively or in addition,one or more features can be standard. The cut guide tool shown in FIG.78 can be designed to rest on 2 mm thick cartilage relative to CT dataand can include a standard tool thickness of 4 mm; however otherstandard thicknesses can be used, for example, a 2 mm or a 3 mmthickness. Moreover, the cut guide tool shown in FIG. 78 can includethree optional pin placements for stabilization and a posterior beam togive stability and rigidity to the tool. The lateral spacer shown on theleft side of FIG. 78 can rest on cut tibia to approximate the thicknessof asymmetry.

The cut tools shown in FIGS. 79A and 79B are designed to follow the cuttool shown in FIG. 78 and can complete the remaining chamfer cuts forthe distal femur. Each of the cut tools shown in the figure includes twopin placements for stabilization. The tool on the left includes shortpegs to be positioned in the peg holes established by a peg hole driverguide tool, for example, as shown in FIGS. 76 and 77. The tool on theright includes no lateral peg to allow for external rotation of theguide tool to establish rotated chamfer cuts.

In certain embodiments, fewer than three guide tools, for example, twoguide tools or one guide tool can be used to establish the peg holes andall the resection cuts associated with installation of a particularimplant component. For example, the single guide tool shown in FIG. 80can be used to establish all the resection cuts associated withinstallation of a femoral implant component, including, for example, adistal cut with one more facets, a posterior cut with one or morefacets, an anterior cut, an anterior chamfer cut with one or morefacets, one or more posterior chamfer cuts each with one or more facets,and one or more step cuts, for example, between two facets of a cut. Theapertures (e.g., holes and slots) in the guide tool and edges of theguide tools can be used to guide peg hole placement and resection cuts.For example, the posterior surface of the guide tool shown in FIG. 80can be used to establish the posterior resection cuts. Optional guidetool attachments can be used to enhance the guidance for one or more ofthe cutting holes or slots in the cut guide tool. For example, theoptional guide tool attachments shown in FIGS. 81A and 81B can be usedto enhance one or more cutting or drilling surfaces.

FIG. 82A shows an additional embodiment of a single guide tool that canbe used to establish the peg holes and all the resection cuts associatedwith installation of a femoral implant component. In particular, thesingle guide tool is presented with three different thicknesses, whichcorresponds to each of images shown on the figure. Having the singleguide tool in different thicknesses allows a surgeon to select theoptimum thickness for balancing before initiating the resection cuts.The guide tool can come in 2, 3, 4, 5, 6, 7, 8, 9, 10, or morethicknesses. One the surgeon has selected the guide tool with theappropriate thickness, the distal resection cut and all subsequentresection cuts can be made using the selected guide tool. This allowsthe distal resection cut to be placed at the appropriate position fromthe joint-line. In addition, FIGS. 82B and 82C show three optional guidetool attachments 8210, 8220, 8230 for enhancing the cutting or drillingsurfaces of the single guide tool. One or more guide tool attachmentscan be used to enhance the cutting and/or drilling surfaces for one,two, more than two, or all of the apertures in a single guide tool. Inthis embodiment, numbers are included on the surface of the guide toolsto indicate the order of the resection cuts. FIG. 82D shows a set ofresection cut guide tools that together can be used to facilitate thesame peg holes and resection cuts that can be facilitated with thesingle guide tool described above. The middle three guide tools (labeledA, B, and C) include the same resection cuts but have differentthicknesses to allow for balancing, as described above. This group ofguide tools can be included in a kit along with the single guide tooldescribed above, for example, to act as a back-up set of guide tools.

FIGS. 82E to 82H show another embodiment of a single guide tool andattachments that can be used to establish the peg holes and all theresection cuts associated with installation of a femoral implantcomponent. In particular, the guide tool shown in FIG. 82E includesthree reinforcement bars between the implant component condyles. Thisguide tool can be presented in one or more thicknesses. As noted above,a guide tool having an appropriate thickness can be used to balance theknee before the surgeon performs any femoral cutting. FIG. 82F shows theguide tool of FIG. 82E with an additional attachment to supplyadditional surface area to guide to a drilling tool in making the twopeg holes. FIG. 82G shows the guide tool of FIG. 82E with an additionalattachment to supply additional surface area to guide a cutting tool inmaking the numbered resection cuts. As shown in the figure, theattachment covers the entire surface area of the guide tool. Theattachment also include flanges adjacent to each cutting hole thatsupply additional surface area for guiding the cutting tool. FIG. 82Hshows the reverse side of the guide tool and attachment shown in FIG.82G. As shown, the attachment can be fixed in place on the guide toolusing an interface that can include fitting a peg from the attachmentinto one or both peg guide holes of the guide tool.

One or more resection cut slots in a particular guide tool can besubstantially, horizontal, substantially diagonal, or substantiallyvertical, for example, as compared to the patient's mechanical axisand/or anatomical axis. Moreover, one or more of the resection cut slotscan allow for a complete resection cut or a partial resection cut, e.g.,scoring of the patient's bone to establish a resection cut that can befinished after removing the tool. This approach can be advantageous byallowing for faster resection in the absence of the guide tool.Moreover, one or more resection cut slots can include a blade-depthstop. This is particularly useful for step resection cuts, for example,vertical step resection cuts, that connect two facets or planes of aresected surface.

8.4 Guide Tool Markings

In certain embodiments, one or more guide tools described herein caninclude markings to identify relevant features, for example, alignmentindicators for anatomical and/or biomechanical axes. Such markings canintraoperatively guide a surgeon in the installation procedure. Forexample, the guide tool shown in FIG. 77 includes on its surfacealignment indicators for the patient's Whiteside's AP trochlear line,the transepicondylar axis (TEA), and the posterior condylar axis (PEA).These indicators can be in colors and/or in raised geometries tostrengthen the guide tool.

Moreover, as shown in FIG. 82A, resection cut apertures on a guide toolcan include numbers or other instructions to direct a surgeon in theproper resection procedure.

Guide tools for establishing tibial resection cuts can include one ormore patient-specific features and/or one or more patient-engineeredfeatures, and/or one or more standard features. For example, thebone-facing surface of a tibial resection guide tool can includepatient-specific features that conform to the uncut tibial surface,e.g., bone and/or cartilage surface. Embodiments of patient-specifictibial resection guide tools are shown in FIGS. 83A to 83H and in FIGS.84A and 84B.

FIGS. 83A to 83F show a tibial guide tool 8310, a tibial guide rod 8320,and a tibial +2 mm additional resection cut guide 8330. The tibial guidetool having a large anterior portion provide a patient-specific surfacearea that matches a portion of the contour of the tibia. The anteriorportion also is relatively thin to make the tool low profile. As shownin the figures, the guide tool includes parallel pins for ease ofremoval and installation, and a cutting slot that extends laterally(e.g., 10 mm laterally) and is 1.32 mm in diameter to better control theblade flex during cutting. In certain embodiments, the tibial guide toolincludes a large medial surface that can be patient-specific for aportion of the patient's corresponding biological structure (e.g., boneor cartilage surface). In this way, the conforming guide tool fitsoptimally on the particular patient's bone and thereby provides a securecutting surface. In certain embodiments, the tibial guide tool caninclude a feature for attaching a tibial guide rod, for example, at theanterior portion of the guide tool. In particular, the tibial guide rodcan mate with the anterior feature of the tibial guide via a rectangularboss and hole. As with the guide tool, the guide rod can include one ormore patient-specific features and/or one or more patient-engineeredfeatures and/or one or more standard features. For the example, thediameter and/or length of the guide rod can be designed based on thespecific patient information, such as information derived from one ormore patient images. The guide rod depicted in the figure includes adiameter of 8.5 mm and a length of 250 mm.

As shown in FIGS. 83G and 83H, one or more additional guide tools can beincluded and used to remove additional bone from the proximal surface ofthe tibia. For example, as shown in the figure, an additional guide toolcan provide a 2 mm deeper resection than is available with a first guidetool. Alternatively, one or more additional guide tools can allow forresection of an additional 1 mm, 3 mm, 4 mm, and/or 5 mm (or any amountin between these values) off the patient's proximal tibia. A singleadditional guide tool can include one or more resection slots to allowfor more than one additional resection depth to be achieved with thatsingle guide tool. The one or more additional guide tools can includeone or more patient-specific features, one or more patient-engineeredfeatures, and one or more standard features.

FIG. 84A shows a tibial guide tool for making the same resection cut asshown for FIGS. 83A to 83F. However, the guide tool shown in FIG. 84Aincludes additional patient-adapted surface area that conforms to thepatient's biological surface. This patient-adapted surface area can bedesigned to conform with the patient's biological structure, e.g.,subchondral bone and/or cartilage surface, based on one or more imagesof the patient's joint. Alternatively, this conforming surface area canbe engineered based on patient-specific images to conform to an expandedoutline of the patient's biological structure, e.g., the patient'ssubchondral bone surface expanded to include estimated amount ofcartilage, for example, expanded 1 mm, 1.5 mm, or 2 mm. For example, theguide tool shown in FIG. 84A can be used to make a 2 mm cut at a 5degree A-P slope. The guide rod can be as described above.

FIG. 84B shows a tibial guide tool to resect into the cut tibial surfaceto create a notch for accepting the keel of a tibial implant component.In certain embodiments, the perimeter of this tool can bepatient-specific to match the perimeter of the patient's cut tibialsurface. In certain embodiments, the perimeter of this tool can matchthe perimeter of the tibial implant component that will rest on the cuttibial surface. Alternatively, the perimeter of this tool can beengineered to be some amount less than the perimeter of the patient'scut tibia. The amount that the perimeter is less that the cut tibia canbe, for example, a percentage of surface area or circumferentialdistance, for example, 2% less, 4% less, 5% less, 6% less, 8% less, 10%less, or some other percent less than the corresponding measure on thepatient's cut tibia. Alternatively, the tibial guide tool and also,optionally, the tibial implant component, can include a perimeter thatis less than the corresponding measure on the patient's cut tibia by anamount calculated to allow for a certain level of intraoperativerotation of the tibial implant component without any overhang of thetibial implant component perimeter.

Various methods can be used to allow for intraoperative rotation of thetibial implant component during installation of the implant. Being ableto rotate and install a rotated tibial implant component can beimportant in balancing the joint with the implant. One example of amethod for intraoperatively preparing a rotated tibial implant componentis shown in FIGS. 85A through 85D. In particular, FIGS. FIGS. 85Athrough 85D show the front and back views of the same tibial guide toolto resect into the cut tibial surface to create a notch for acceptingthe keel of a tibial implant component. FIGS. FIGS. 85B through 85D eachadditionally show an insert with holes for guiding a drilling tool. Theholes in each figure are oriented at different angles. Specifically, theinsert in FIG. 85B can create holes at a 0 degree rotation angle; theinsert in FIG. 85C can create holes at a 5 degree rotation angle; andthe insert in FIG. 85D can create holes at a 5 degree rotation angle.Accordingly, by supplying along with the guide tool a series of insertswith holes at various angles, the resected holes and subsequent notchcan be rotated at any desired angle (for which an insert has beensupplied), which in turn will rotate the tibial implant component by thesame angle as its keel is placed into the notch. Inserts can be includedto have any degree of rotated holes, for example, inserts can beincluded to rotate the notch and implant 1, 2, 3, 4, 5, 6, 7, 8, 9, 10degrees or more. Any number of inserts with different hole rotations canbe included. In certain embodiments, the a maximum rotation for a giventibial implant component can be calculated as the rotation at which anundersized component perimeter extends beyond (i.e., overhangs) theperimeter of the patient's cut tibial surface, and inserts can belimited to this maximum rotation. FIGS. 86A through 86D show the samefront view of the guide tools and inserts shown in FIGS. 85A through 85Dand, in addition, show front and back view of three exemplary inserts.As shown in the figures, in certain embodiments the inserts can includedifferently keyed insert shapes.

9. Manufacturing

The step of designing an implant component and/or guide tool asdescribed herein can include both configuring one or more features,measurements, and/or dimensions of the implant and/or guide tool (e.g.,derived from patient-specific data from a particular patient and adaptedfor the particular patient) and manufacturing the implant. In certainembodiments, manufacturing can include making the implant componentand/or guide tool from starting materials, for example, metals and/orpolymers or other materials in solid (e.g., powders or blocks) or liquidform. In addition or alternatively, in certain embodiments,manufacturing can include altering (e.g., machining) an existing implantcomponent and/or guide tool, for example, a standard blank implantcomponent and/or guide tool or an existing implant component and/orguide tool (e.g., selected from a library). The manufacturing techniquesto making or altering an implant component and/or guide tool can includeany techniques known in the art today and in the future. Such techniquesinclude, but are not limited to additive as well as subtractive methods,i.e., methods that add material, for example to a standard blank, andmethods that remove material, for example from a standard blank.

Various technologies appropriate for this purpose are known in the art,for example, as described in Wohlers Report 2009, State of the IndustryAnnual Worldwide Progress Report on Additive Manufacturing, WohlersAssociates, 2009 (ISBN 0-9754429-5-3), available from the webwww.wohlersassociates.com; Pham and Dimov, Rapid manufacturing,Springer-Verlag, 2001 (ISBN 1-85233-360-X); Grenda, Printing the Future,The 3D Printing and Rapid Prototyping Source Book, Castle Island Co.,2009; Virtual Prototyping & Bio Manufacturing in Medical Applications,Bidanda and Bartolo (Eds.), Springer, Dec. 17, 2007 (ISBN: 10:0387334297; 13: 978-0387334295); Bio-Materials and PrototypingApplications in Medicine, Bártolo and Bidanda (Eds.), Springer, Dec. 10,2007 (ISBN: 10: 0387476822; 13: 978-0387476827); Liou, Rapid Prototypingand Engineering Applications: A Toolbox for Prototype Development, CRC,Sep. 26, 2007 (ISBN: 10: 0849334098; 13: 978-0849334092); AdvancedManufacturing Technology for Medical Applications Reverse Engineering,Software Conversion and Rapid Prototyping, Gibson (Ed.), Wiley, January2006 (ISBN: 10: 0470016884; 13: 978-0470016886); and Branner et al.,“Coupled Field Simulation in Additive Layer Manufacturing,” 3rdInternational Conference PMI, 2008 (10 pages).

Exemplary techniques for adapting an implant to a patient's anatomyinclude, but are not limited to those shown in Table 18.

TABLE 18 Exemplary techniques for forming or altering a patient-specificand/or patient-engineered implant component for a patient's anatomyTechnique Brief description of technique and related notes CNC CNCrefers to computer numerically controlled (CNC) machine tools, acomputer-driven technique, e.g., computer-code instructions, in whichmachine tools are driven by one or more computers. Embodiments of thismethod can interface with CAD software to streamline the automateddesign and manufacturing process. CAM CAM refers to computer-aidedmanufacturing (CAM) and can be used to describe the use of softwareprogramming tools to efficiently manage manufacturing and production ofproducts and prototypes. CAM can be used with CAD to generate CNC codefor manufacturing three-dimensional objects. Casting, including Castingis a manufacturing technique that employs a mold. casting using rapidTypically, a mold includes the negative of the desired shape of aprototyped casting product. A liquid material is poured into the moldand allowed to patterns cure, for example, with time, cooling, and/orwith the addition of a solidifying agent. The resulting solid materialor casting can be worked subsequently, for example, by sanding orbonding to another casting to generate a final product. Welding Weldingis a manufacturing technique in which two components are fused togetherat one or more locations. In certain embodiments, the component joiningsurfaces include metal or thermoplastic and heat is administered as partof the fusion technique. Forging Forging is a manufacturing technique inwhich a product or component, typically a metal, is shaped, typically byheating and applying force. Rapid prototyping Rapid prototyping refersgenerally to automated construction of a prototype or product, typicallyusing an additive manufacturing technology, such as EBM, SLS, SLM, SLA,DMLS, 3DP, FDM and other technologies EBM ® EBM ® refers to electronbeam melting (EBM ®), which is a powder- based additive manufacturingtechnology. Typically, successive layers of metal powder are depositedand melted with an electron beam in a vacuum. SLS SLS refers toselective laser sintering (SLS), which is a powder-based additivemanufacturing technology. Typically, successive layers of a powder(e.g., polymer, metal, sand, or other material) are deposited and meltedwith a scanning laser, for example, a carbon dioxide laser. SLM SLMrefers to selective laser melting ™ (SLM), which is a technology similarto SLS; however, with SLM the powder material is fully melted to form afully-dense product. SLA or SL SLA or SL refers to stereolithography(SLA or SL), which is a liquid- based additive manufacturing technology.Typically, successive layers of a liquid resin are exposed to a curing,for example, with UV laser light, to solidify each layer and bond it tothe layer below. This technology typically requires the additional andremoval of support structures when creating particular geometries. DMLSDMLS refers to direct metal laser sintering (DMLS), which is apowder-based additive manufacturing technology. Typically, metal powderis deposited and melted locally using a fiber optic laser. Complex andhighly accurate geometries can be produced with this technology. Thistechnology supports net-shaping, which means that the product generatedfrom the technology requires little or no subsequent surface finishing.LC LC refers to LaserCusing ®(LC), which is a powder-based additivemanufacturing technology. LC is similar to DMLS; however, with LC ahigh-energy laser is used to completely melt the powder, therebycreating a fully-dense product. 3DP 3DP refers to three-dimensionalprinting (3DP), which is a high- speed additive manufacturing technologythat can deposit various types of materials in powder, liquid, orgranular form in a printer-like fashion. Deposited layers can be curedlayer by layer or, alternatively, for granular deposition, anintervening adhesive step can be used to secure layered granulestogether in bed of granules and the multiple layers subsequently can becured together, for example, with laser or light curing. LENS LENS ®refers to Laser Engineered Net Shaping ™ (LENS ®), which is apowder-based additive manufacturing technology. Typically, a metalpowder is supplied to the focus of the laser beam at a deposition head.The laser beam melts the powder as it is applied, in raster fashion. Theprocess continues layer by and layer and requires no subsequent curing.This technology supports net-shaping, which means that the productgenerated from the technology requires little or no subsequent surfacefinishing. FDM FDM refers to fused deposition modeling ™ (FDM) is anextrusion- based additive manufacturing technology. Typically, beads ofheated extruded polymers are deposited row by row and layer by layer.The beads harden as the extruded polymer cools.

9.1 Implant Components Generated from Different Manufacturing Methods

Implant components generated by different techniques can be assessed andcompared for their accuracy of shape relative to the intended shapedesign, for their mechanical strength, and for other factors. In thisway, different manufacturing techniques can supply another considerationfor achieving an implant component design with one or more targetfeatures. For example, if accuracy of shape relative to the intendedshape design is critical to a particular patient's implant componentdesign, then the manufacturing technique supplying the most accurateshape can be selected. If a minimum implant thickness is critical to aparticular patient's implant component design, then the manufacturingtechnique supplying the highest mechanical strength and thereforeallowing the most minimal implant component thickness, can be selected.Branner et al. describe a method a method for the design andoptimization of additive layer manufacturing through a numericalcoupled-field simulation, based on the finite element analysis (FEA).Branner's method can be used for assessing and comparing productmechanical strength generated by different additive layer manufacturingtechniques, for example, SLM, DMLS, and LC.

In certain embodiments, an implant can include components and/or implantcomponent parts produced via various methods. For example, in certainembodiments for a knee implant, the knee implant can include a metalfemoral implant component produced by casting or by an additivemanufacturing technique and having a patient-specific femoralintercondylar distance; a tibial component cut from a blank and machinedto be patient-specific for the perimeter of the patient's cut tibia; anda tibial insert having a standard lock and a top surface that ispatient-specific for at least the patient's intercondylar distancebetween the tibial insert dishes to accommodate the patient-specificfemoral intercondylar distance of the femoral implant.

As another example, in certain embodiments a knee implant can include ametal femoral implant component produced by casting or by an additivemanufacturing technique that is patient-specific with respect to aparticular patient's M-L dimension and standard with respect to thepatient's femoral intercondylar distance; a tibial component cut from ablank and machined to be patient-specific for the perimeter of thepatient's cut tibia; and a tibial insert having a standard lock and atop surface that includes a standard intercondylar distance between thetibial insert dishes to accommodate the standard femoral intercondylardistance of the femoral implant.

9.2 Repair Materials

A wide variety of materials find use in the practice of the embodimentsdescribed herein, including, but not limited to, plastics, metals,crystal free metals, ceramics, biological materials (e.g., collagen orother extracellular matrix materials), hydroxyapatite, cells (e.g., stemcells, chondrocyte cells or the like), or combinations thereof. Based onthe information (e.g., measurements) obtained regarding the defect andthe articular surface and/or the subchondral bone, a repair material canbe formed or selected. Further, using one or more of these techniquesdescribed herein, a cartilage replacement or regenerating materialhaving a curvature that will fit into a particular cartilage defect,will follow the contour and shape of the articular surface, and willmatch the thickness of the surrounding cartilage. The repair materialcan include any combination of materials, and typically includes atleast one non-pliable material, for example materials that are noteasily bent or changed.

Currently, joint repair systems often employ metal and/or polymericmaterials including, for example, prostheses which are anchored into theunderlying bone (e.g., a femur in the case of a knee prosthesis). See,e.g., U.S. Pat. No. 6,203,576 to Afriat et al. issued Mar. 20, 2001 andU.S. Pat. No. 6,322,588 to Ogle, et al. issued Nov. 27, 2001, andreferences cited therein. A wide-variety of metals is useful in thepractice of the embodiments described herein, and can be selected basedon any criteria. For example, material selection can be based onresiliency to impart a desired degree of rigidity. Non-limiting examplesof suitable metals include silver, gold, platinum, palladium, iridium,copper, tin, lead, antimony, bismuth, zinc, titanium, cobalt, stainlesssteel, nickel, iron alloys, cobalt alloys, such as Elgiloy®, acobalt-chromium-nickel alloy, and MP35N, anickel-cobalt-chromiummolybdenum alloy, and Nitinol T™, anickel-titanium alloy, aluminum, manganese, iron, tantalum, crystal freemetals, such as Liquidmetal® alloys (available from LiquidMetalTechnologies, www.liquidmetal.com), other metals that can slowly formpolyvalent metal ions, for example to inhibit calcification of implantedsubstrates in contact with a patient's bodily fluids or tissues, andcombinations thereof

Suitable synthetic polymers include, without limitation, polyamides(e.g., nylon), polyesters, polystyrenes, polyacrylates, vinyl polymers(e.g., polyethylene, polytetrafluoroethylene, polypropylene andpolyvinyl chloride), polycarbonates, polyurethanes, poly dimethylsiloxanes, cellulose acetates, polymethyl methacrylates, polyether etherketones, ethylene vinyl acetates, polysulfones, nitrocelluloses, similarcopolymers and mixtures thereof. Bioresorbable synthetic polymers canalso be used such as dextran, hydroxyethyl starch, derivatives ofgelatin, polyvinylpyrrolidone, polyvinyl alcohol,poly[N-(2-hydroxypropyl)methacrylamide], poly(hydroxy acids),poly(epsilon-caprolactone), polylactic acid, polyglycolic acid,poly(dimethyl glycolic acid), poly(hydroxy butyrate), and similarcopolymers.

Other appropriate materials include, for example, the polyketone knownas polyetheretherketone (PEEKT). This includes the material PEEK 450G,which is an unfilled PEEK approved for medical implantation availablefrom Victrex of Lancashire, Great Britain. (Victrex is located atwww.matweb.com or see Boedeker www.boedeker.com). Other sources of thismaterial include Gharda located in Panoli, India(www.ghardapolymers.com).

It should be noted that the material selected can also be filled. Forexample, other grades of PEEK are also available and contemplated, suchas 30% glass-filled or 30% carbon filled, provided such materials arecleared for use in implantable devices by the FDA, or other regulatorybody. Glass filled PEEK reduces the expansion rate and increases theflexural modulus of PEEK relative to that portion which is unfilled. Theresulting product is known to be ideal for improved strength, stiffness,or stability. Carbon filled PEEK is known to enhance the compressivestrength and stiffness of PEEK and lower its expansion rate. Carbonfilled PEEK offers wear resistance and load carrying capability.

As will be appreciated, other suitable similarly biocompatiblethermoplastic or thermoplastic polycondensate materials that resistfatigue, have good memory, are flexible, are deflectable, have very lowmoisture absorption, and/or have good wear and/or abrasion resistance,can be used. The implant can also be comprised of polyctherketoneketone(PEKK).

Other materials that can be used include polyetherketone (PEK),polyetherketoneetherketoneketone (PEKEKK), andpolyetheretherketoneketone (PEEKK), and, generally, apolyaryletheretherketone. Further, other polyketones can be used as wellas other thermoplastics.

Reference to appropriate polymers that can be used for the implant canbe made to the following documents, all of which are incorporated hereinby reference. These documents include: PCT Publication WO 02/02158 A1,dated Jan. 10, 2002 and entitled Bio-Compatible Polymeric Materials; PCTPublication WO 02/00275 A1, dated Jan. 3, 2002 and entitledBio-Compatible Polymeric Materials; and PCT Publication WO 02/00270 A1,dated Jan. 3, 2002 and entitled Bio-Compatible Polymeric Materials.

The polymers can be prepared by any of a variety of approaches includingconventional polymer processing methods. Preferred approaches include,for example, injection molding, which is suitable for the production ofpolymer components with significant structural features, and rapidprototyping approaches, such as reaction injection molding andstereo-lithography. The substrate can be textured or made porous byeither physical abrasion or chemical alteration to facilitateincorporation of the metal coating. Other processes are alsoappropriate, such as extrusion, injection, compression molding and/ormachining techniques. Typically, the polymer is chosen for its physicaland mechanical properties and is suitable for carrying and spreading thephysical load between the joint surfaces.

More than one metal and/or polymer can be used in combination with eachother. For example, one or more metal-containing substrates can becoated with polymers in one or more regions or, alternatively, one ormore polymer-containing substrate can be coated in one or more regionswith one or more metals.

The system or prosthesis can be porous or porous coated. The poroussurface components can be made of various materials including metals,ceramics, and polymers. These surface components can, in turn, besecured by various means to a multitude of structural cores formed ofvarious metals. Suitable porous coatings include, but are not limitedto, metal, ceramic, polymeric (e.g., biologically neutral elastomerssuch as silicone rubber, polyethylene terephthalate and/or combinationsthereof or combinations thereof. See, e.g., U.S. Pat. No. 3,605,123 toHahn, issued Sep. 20, 1971. U.S. Pat. No. 3,808,606 to Tronzo issued May7, 1974 and U.S. Pat. No. 3,843,975 to Tronzo issued Oct. 29, 1974; U.S.Pat. No. 3,314,420 to Smith issued Apr. 18, 1967; U.S. Pat. No.3,987,499 to Scharbach issued Oct. 26, 1976; and GermanOffenlegungsschrift 2,306,552. There can be more than one coating layerand the layers can have the same or different porosities. See, e.g.,U.S. Pat. No. 3,938,198 to Kahn, et al., issued Feb. 17, 1976.

The coating can be applied by surrounding a core with powdered polymerand heating until cured to form a coating with an internal network ofinterconnected pores. The tortuosity of the pores (e.g., a measure oflength to diameter of the paths through the pores) can be important inevaluating the probable success of such a coating in use on a prostheticdevice. See, also, U.S. Pat. No. 4,213,816 to Morris issued Jul. 22,1980. The porous coating can be applied in the form of a powder and thearticle as a whole subjected to an elevated temperature that bonds thepowder to the substrate. Selection of suitable polymers and/or powdercoatings can be determined in view of the teachings and references citedherein, for example based on the melt index of each.

EXAMPLES

Example 1 describes an exemplary process for designing a patient-adaptedimplant component. Example 2 describes an exemplary patient-adapted kneeimplants components and methods for designing the same. Example 3describes exemplary knee implants components having patient-adaptedfeatures and non-traditional features. Example 4 illustrates an implantand implant design having straight and curvilinear bone cuts. Example 5illustrates an implant and implant design having resurfacing and one orno bone cuts. Example 6 describes an exemplary femoral implant componenthaving non-traditional bone cuts on its inner, bone-facing surface.Example 7 describes an exemplary femoral implant component with anenhanced articular surface. Example 8 illustrates a patient-adaptedimplant design for an implant having a femoral component and a patellacomponent. Example 9 illustrates an exemplary process for virtuallyaligning a patient's lower extremity, in preparation for designing aknee implant component. Example 10 illustrates a finite element analysis(“FEA”) used to design and/or assess an implant component.

Example 11 describes and exemplary tibial implant design and relatedresection techniques. Example 12 describes exemplary tibial tray andinsert designs and related jigs and cutting designs. Example 13describes an exemplary design for a tibial implant component.

Example 14 illustrates a set of jigs for guiding patient-specific bonecuts in a femur-first technique. Example 15 illustrates a set of jigsfor guiding patient-specific bone cuts in a tibia-first technique.

Example 1 Exemplary Design Process for Certain Patient-Specific TotalKnee Implants

This example describes an exemplary process for selecting and/ordesigning a patient-adapted total knee implant, for example, a kneeimplant having one or more patient-specific and/or patient-engineeredbased on patient-specific data. The steps described in this process canbe performed in any order and can be performed more than once in aparticular process. For example, one or more steps can be reiterated andrefined a second, third, or more times, before, during, or afterperforming other steps or sets of steps in the process. While thisprocess specifically describes steps for selecting and/or designing apatient-specific total knee implant, it can be adapted to design otherembodiments, for example, patient-adapted bicompartmental knee implants,unicompartmental knee implants, and implants for shoulders and hips,vertebrae, and other joints.

1.1 Methods

The exemplary process shown in FIG. 87 includes four general steps and,optionally, can include a fifth general step. Each general step includesvarious specific steps. The general steps are identified as (1)-(5) inthe figure. These steps can be performed virtually, for example, byusing one or more computers that have or can receive patient-specificdata and specifically configured software or instructions to performsuch steps.

In general step (1), limb alignment and deformity corrections aredetermined, to the extent that either is needed for a specific patient'ssituation. In general step (2), the requisite tibial and femoraldimensions of the implant components are determined based onpatient-specific data obtained, for example, from image data of thepatient's knee.

In general step (3), bone preservation is maximized by virtuallydetermining a resection cut strategy for the patient's femur and/ortibia that provides minimal bone loss optionally while also meetingother user-defined parameters such as, for example, maintaining aminimum implant thickness, using certain resection cuts to help correctthe patient's misalignment, removing diseased or undesired portions ofthe patient's bone or anatomy, and/or other parameters. This generalstep can include one or more of the steps of (i) simulating resectioncuts on one or both articular sides (e.g., on the femur and/or tibia),(ii) applying optimized cuts across one or both articular sides, (iii)allowing for non-co-planar and/or non-parallel femoral resection cuts(e.g., on medial and lateral corresponding portions of the femur) and,optionally, non-co-planar and/or non-parallel tibial resection cuts(e.g., on medial and lateral corresponding portions of the tibia), and(iv) maintaining and/or determining minimal material thickness. Theminimal material thickness for the implant selection and/or design canbe an established threshold, for example, as previously determined by afinite element analysis (“FEA”) of the implant's standardcharacteristics and features. Alternatively, the minimal materialthickness can be determined for the specific implant, for example, asdetermined by an FEA of the implant's standard and patient-specificcharacteristics and features. This step identifies for a surgeon thebone resection design to perform in the surgical theater and it alsoidentifies the design of the bone-facing surface(s) of the implantcomponents, which substantially negatively-match the patient's resectedbone surfaces, at least in part.

In general step (4), a corrected, normal and/or optimized articulargeometry on the femur and tibia is recreated virtually. For the femur,this general step can include, for example, the step of: (i) selecting astandard sagittal profile, or selecting and/or designing apatient-engineered or patient-specific sagittal profile; and (ii)selecting a standard coronal profile, or selecting and/or designing apatient-specific or patient-engineered coronal profile. Optionally, thesagittal and/or coronal profiles of one or more corresponding medial andlateral portions (e.g., medial and lateral condyles) can includedifferent curvatures. For the tibia, this general step includes one orboth of the steps of: (iii) selecting a standard anterior-posteriorslope, and/or selecting and/or designing a patient-specific orpatient-engineered anterior-posterior slope, either of which optionallycan vary from medial to lateral sides; and (iv) selecting a standardpoly-articular surface, or selecting and/or designing a patient-specificor patient-engineered poly-articular surface. The patient-specificpoly-articular surface can be selected and/or designed, for example, tosimulate the normal or optimized three-dimensional geometry of thepatient's tibial articular surface. The patient-engineeredpoly-articular surface can be selected and/or designed, for example, tooptimize kinematics with the bearing surfaces of the femoral implantcomponent. This step can be used to define the bearing portion of theouter, joint-facing surfaces (i.e., articular surfaces) of the implantcomponents.

In optional general step (5), a virtual implant model (for example,generated and displayed using a computer specifically configured withsoftware and/or instructions to assess and display such models) isassessed and can be altered to achieve normal or optimized kinematicsfor the patient. For example, the outer joint-facing or articularsurface(s) of one or more implant components can be assessed and adaptedto improve kinematics for the patient. This general step can include oneor more of the steps of: (i) virtually simulating biomotion of themodel, (ii) adapting the implant design to achieve normal or optimizedkinematics for the patient, and (iii) adapting the implant design toavoid potential impingement.

1.2 Results and Discussion

The exemplary process described above yields both a predeterminedsurgical resection design for altering articular surfaces of a patient'sbones during surgery and a design for an implant that specifically fitsthe patient, for example, following the surgical bone resectioning.Specifically, the implant selection and/or design, which can includemanufacturing or machining the implant to the selected and/or designedspecifications using known techniques, includes one or morepatient-engineered bone-facing surfaces that negatively-match thepatient's resected bone surface. The implant also can include otherfeatures that are patient-adapted, such as minimal implant thickness,articular geometry, and kinematic design features. This process can beapplied to various joint implants and to various types of jointimplants. For example, this design process can be applied to a totalknee, cruciate retaining, posterior stabilized, and/or ACL/PCL retainingknee implants, bicompartmental knee implants, unicompartmental kneeimplants, and other joint implants, for example, for the shoulder, hip,elbow, spine, or other joints.

The exemplary process described above, including the resultingpatient-adapted implants and predetermined bone resectioning design,offers several advantages over traditional primary and revision implantsand related processes. For example, it allows for one or morepre-primary implants such that a subsequent replacement or improvementcan take the form of a primary implant. Specifically, because theprocess described herein can minimize the amount of bone that isresected, enough bone stock may remain such that a subsequent proceduremay be performed with a traditional, primary, off-the-shelf implant.This offers a significant advantage for younger patients who may requirein their lifetime more than a single revision for an implant. In fact,the exemplary process described above may allow for two or morepre-primary implants or procedures before so much bone stock issacrificed that a traditional, primary implant is required.

The advantageous minimal bone resectioning and therefore minimal boneloss that is achieved with this process arises from the fact that thebone-facing surfaces of the implants are derived for each patient basedon patient-specific data, such as, for example, data derived from imagesof the patient's joint, size or weight of the patient, size of thejoint, and size, shape and/or severity of defects and/or disease in thejoint. This patient-adapted approach allows for the bone-facing surfaceof the implant components to be optimized with respect to any number ofparameters, including minimizing bone loss, using any number ofresection cuts and corresponding implant component bone cuts and bonecut facets to conserve bone for the patient. With traditional implants,the implant's bone-facing surface includes standard bone cuts and theresection cuts to the patient's bone are made to fit those standard bonecuts.

Another advantage to this process is that the selection and/or designprocess can incorporate any number of target parameters such that anynumber of implant component features and resection cuts can be selectedand/or designed to meet one or more parameters that are predetermined tohave clinical value. For example, in addition to bone preservation, aselection and/or design process can include target parameters to restorea patient's native, normal kinematics, or to provide optimizedkinematics. For example, the process for selecting and/or designing animplant and/or resection cuts can include target parameters such asreducing or eliminating the patient's mid-flexion instability, reducingor eliminating “tight” closure, improving or extending flexion,improving or restoring cosmetic appearance, and/or creating or improvingnormal or expected sensations in the patient's knee. The design for atibial implant can provide an engineered surface that replicates thepatient's normal anatomy yet also allows for low contact stress on thetibia.

For surgeons and medical professionals, this process also provides asimplified surgical technique. The selected and/or designed bone cutsand, optionally, other features that provide a patient-adapted fit forthe implant components eliminates the complications that arise in thesurgical setting with traditional, misfitting implants. Moreover, sincethe process and implant component features are predetermined prior tosurgery, model images of the surgical steps can be provided to thesurgeon as a guide.

As noted above, the design of an implant component can includemanufacturing or machining the component in accordance with the implantdesign specifications. Manufacturing can include, for example, using adesigned mold to form the implant component. Machining can include, forexample, altering a selected blank form to conform to the implant designspecifications. For example, using the steps described above, thefemoral implant component can be manufactured from a designed mold andthe tibial implant component, including each of a tibial tray andinsert, can be customized from a selected starting tray and insert, forexample, from blanks.

Example 2 Patient-Adapted Femoral Implant Component with Five Bone Cutsand Corresponding Resection Cuts

This example describes two exemplary methods for designing resectioncuts to a patient's femur and related bone cuts on the bone-facingsurface of a femoral implant component designed for the patient. Inparticular, in both methods, a model of a patient's distal femur iscreated based on data from patient-specific two- or three-dimensionalimages of the patient's femur. As shown in FIG. 88A, the epicondylaraxis 8810 is determined for the patient's femur. Then, the resection cutplanes and cut angles (and corresponding implant component cut planesand cut angles) are assessed and selected using the epicondylar axis8810 as a reference. Specifically, four of the five cut planes—thedistal cut, posterior cut, posterior chamfer cut, and anterior chamfercut—are designed to be parallel with the epicondylar axis 8810. FIG. 88Ashows the distal cut plane 8820 parallel to the epicondylar axis 8810.However, for the particular patient, the anterior cut plane is designedto be oblique to the epicondylar axis 8810, which can minimize theamount of bone resected on the lateral side of the cut. FIG. 88B showsan example of an anterior oblique cut plane 8830.

For each of the five cut planes, optimized cuts (i.e., resection cuts)tangent to the bone surface at the angle of each resection plane also isdetermined. The optimized cuts as shown in FIGS. 89A to 89E included amaximum cut depth of 6 mm for the distal cut plane (FIG. 89A), theanterior chamfer cut plane (FIG. 89B), the posterior chamfer cut (FIG.89C), and the posterior cut plane (FIG. 89D). The maximum cut depth is 5mm for the anterior cut plane (FIG. 89E). Optimized cuts can bedetermined based on one or more parameters, including those describedabove. In this example, optimized cut were determined, at least in part,to minimize resected bone while providing greater than a thresholdminimum implant thickness. Deeper resection cuts allow for a thickerimplant, but require greater bone loss. Typically, the thinnestresection cut depth and, accordingly, the minimum implant thicknessoccurs at the intersections between cut planes. Accordingly,alternatively or in addition to altering cut plane depths, the number ofcut planes, the cut plane angles and/or the cut plane orientations canbe altered to provide deeper cut plane intersections and correspondinggreater minimum implant thickness at the bone cut intersections whilealso minimizing the amount of bone resected from the patient.

The optimized number of cut planes, depths of cut planes, angles of cutplanes and/or orientations of cut planes can be determined independentlyfor each of the medial and lateral femoral condyles. For example, FIGS.89A to 89E show optimized cut planes based on the medial condyle.However, FIGS. 90A and 90B show cut planes for the lateral condyleposterior chamfer (FIG. 90A) and lateral condyle posterior (FIG. 90B)cut planes that are independently optimized (i.e., relative to themedial condyle posterior chamfer and medial condyle posterior cutplanes, respectively) based on patient-specific data for the lateralcondyle. This type of independent optimization between condyles canresult in a different number of cut plane facets, different angles ofcut plane facets, and/or different depths of cut plane facets oncorresponding portions of medial and lateral condyles.

Two exemplary resection cut designs (and corresponding implant componentbone cut design e.g., that includes substantially matching cut featuresof the resection cut design) is based on five cut planes are describedin this example. In the first design, shown in FIG. 91A, a distal cutplane is designed perpendicular to the sagittal femoral axis 9100. Inthe second design, referred to as a “flexed” or “flex-fit” design” andshown in FIG. 91B, the distal cut plane is rotated 15 degrees in flexionfrom the perpendicular to the sagittal femoral axis. The additional fourcut planes are shifted accordingly for each design method, as shown inFIGS. 92A and 92B.

FIGS. 93A and 93B show the completed cut femur models for each cutdesign. For each design, the maximum resection depth for each cut planewas 6 mm, except for the anterior cut plane, which was 5 mm. The“flex-fit” design can provide more posterior coverage in high flexion.However, it also may require more anterior bone resectioning to achievesufficient coverage and may require particular attention during actualbone cutting to avoid any incomplete bone removal at the trochlear notch9310. In certain embodiments of a cut plane design, the anterior andposterior cut planes diverge from the component peg axis by five degreeseach, as shown in FIG. 94A. With a traditional femoral implantcomponent, the posterior and anterior cut planes diverge 2 degrees and 7degrees, respectively, from the peg axis. Moreover, in certainembodiments, the peg can be designed to have various dimensions. Forexample, the design in FIG. 94B includes a peg diameter of 7 mm taperingto about 6.5 mm, a length of 14 mm with a rounded tip, and a base with a1 mm fillet 9410.

An exemplary bone facing surface of the femoral implant component designis shown in FIGS. 95A and 95B. In addition to optimized cut planesdescribed above, these implant components also include a patient-adaptedperipheral margin 9510 that is 0.5 mm from the edge of cut bone. Thedesigns also can include engineered coronal curvatures on the condyles.Side views of the resulting femoral implant component designs for thefirst and second design methods are shown in FIGS. 96A and 96B. Thissagittal view of the implant components shows the difference in anteriorand posterior coverage for the two designs. As seen by a comparison ofthe two figures, the flexed cut design provides greater posteriorcoverage, which enhances deep knee flexion for the patient. Accordingly,as shown by this example, one or more features or measurements derivedfrom patient-specific data are used to preoperatively select and/ordesign implant component features that target and achieve more than oneparameter, in this case preservation of the patient's bone andpreservation, restoration, or enhancement of the patient's jointkinematics.

As mentioned above, the optimization of resection cuts and implantcomponent bone cuts can result in a cut design that has any number ofcut planes or facets, depths of cut planes or facets, angles of cutplanes or facets, and/or orientations of cut planes or facets. Inaddition to optimizing the cut planes to minimize bone loss and maximizeimplant thickness, various other parameters can be included in the cutplane optimization. In this example, the flexed cut design was used tohelp preserve, restore, or enhance the patient's joint kinematics.Additional parameters that may be included in the determination ofoptimized resection and bone cuts can include, but are not limited to,one or more of: (1) deformity correction and/or limb alignment (2)maximizing preservation of cartilage, or ligaments, (3) maximizingpreservation and/or optimization of other features of the patient'sanatomy, such as trochlea and trochlear shape, (4) further restorationand/or optimization of joint kinematics or biomechanics (5) restorationor optimization of joint-line location and/or joint gap width, and (6)preservation, restoration, or enhancement of other target features.

Example 3 Design of a Femoral Component of a Total Knee Replacement witha Bone-Facing Surface that Optimizes Bone Preservation

This example describes an exemplary design of femoral implant component.In particular, the femoral component includes seven bone cuts on itsinner, bone-facing surface.

3.1 Methods

A femoral implant component (PCL-retaining) is designed with seven bonecuts for a femur-first implantation technique. The design of the implantcomponent is depicted in FIG. 97. The seven bone cuts on the inner,bone-facing surface of the implant component include a distal bone cut9701 (including lateral and medial facets) that is perpendicular to thesagittal femoral axis, and an anterior cut 9702. The correspondingresection cut planes are shown in FIG. 98A and in FIG. 98B.Specifically, a first anterior chamfer cut plane is at 25 degrees, asecond anterior chamfer cut plane is at 57 degrees, and an anterior cutplane is at 85 degrees relative to the distal femoral cut plane, asshown in FIG. 98A. Moreover, a first posterior chamfer cut plane is at25 degrees, a second posterior chamfer cut plane is at 57 degrees, and aposterior chamfer cut plane is at 87 degrees relative to the distalfemoral cut plane, as shown in FIG. 98B. The femoral implant includesbone cuts that substantially negatively-match (e.g., in cut angle, area,and/or orientation) the resection cuts on these cut planes. The femoralimplant component also can include on its bone-facing surface cementcutouts 9704 that are 0.5 mm deep and offset from the outer edge by 2mm, and a peg protruding from the each of the lateral and medial distalbone cuts facets. The pegs are 7 mm in diameter, 17 mm long and aretapered by 0.5 degrees as they extend from the component. FIG. 99 showsthe cement pocket and peg features.

3.2 Results and Discussion

In a traditional femoral implant component, the bone-facing surfaceconsists of five standard bone cuts. However, the femoral component inthis example includes seven bone cuts on the bone-facing surface. Theadditional bone cuts can allow for the corresponding resection cutplanes be less deep from the bone surface to insure that the cut planeintersections have a depth below the bone surface that allows for aminimum implant thickness. Accordingly, less bone can be resected for aseven-bone-cut implant component than for a traditional five-bone-cutimplant component to provide the same minimum implant componentthickness, e.g., at the bone cut intersections. Moreover, the outer,joint-facing surface of the implant component described in this exampleincludes a combination of patient-adapted features and standardfeatures.

FIG. 100A shows a five-cut-plane femoral resection design for a femoralimplant component having five bone cuts. FIG. 100B shows aseven-cut-plane femoral resection design for a femoral implant componenthaving seven bone cuts. Each cut design was performed on the samepatient femur model (i.e., having identical bone volumes). In addition,the corresponding five-bone-cut implant component and seven-bone-cutimplant component were both designed meet or exceed the same minimumimplant thickness. After performing the resection cuts, the model of thepatient's femur having five resection cuts retained bone volume of103,034 mm³, while the model of the patient's femur having seven bonecuts retained a bone volume of 104,220 mm³. As this analysis shows, theseven-bone-cut implant component saved substantially more of thepatient's bone stock, in this case more than 1,000 mm³, as compared tothe five-bone cut implant component.

A similar analysis was performed to assess relative bone loss between afive-cut design and a five-flexed cut design. FIG. 101A shows apatient's femur having five, not flexed resection cuts and FIG. 101Bshows the same femur but with five, flexed resection cuts. As shown, themodel having five, not flexed resection cuts retains a bone volume of109,472 mm³, while the model having five, flexed resection cuts retainsa bone volume of 105,760 mm³. As this analysis shows, thenot-flexed-five-bone-cut implant component saved substantially more ofthe patient's bone stock, in this case nearly 4,000 mm³, as compared tothe flexed-five-bone-cut cut implant component. However, as noted inExample 2, the flexed cut design can offer other advantages, such asgreater posterior coverage and enhanced deep-knee flexion, which can beweighed relative to all selected parameters and accordingly integratedin the selection and/or design of an implant component.

FIGS. 102A to 102D show outlines of a traditional five-cut femoralcomponent (in hatched lines) overlaid with, in 102A, a femur havingseven optimized resection cuts for matching an optimized seven-bone-cutimplant component; in FIG. 102B, a femur having five optimized resectioncuts for matching to an optimized five-bone-cut implant component; inFIG. 102C, a femur having five, not flexed resection cuts for matchingto an optimized five-bone-cut implant component; and in FIG. 102D, afemur having five, flexed resection cuts for matching to an optimizedfive-bone-cut, flexed implant component. As shown in each of thesefigures, the designed bone cuts save substantial bone as compared tothose required by a traditional implant component.

In summary, the component designs described in this example can savepatient bone stock as compared to a traditional implant component andthereby allow the implant to be pre-primary. Alternatively or inaddition, the implant components may include cut planes (i.e., ofresection cuts and bone cuts) that are optimized based onpatient-specific data to meet one or more user-defined parameters, asdescribed above. For example, cut planes can be symmetric or asymmetric,parallel or non-parallel, aligned perpendicular to the sagittal plane ornot perpendicular, varied from medial to lateral condyle, and/or caninclude other orientations. The cut plane designs may include a “flexed”(i.e., rotated or offset relative to the biomechanical or anatomicalaxes) orientation. Moreover, the design of attachment pegs may also beflexed relative to the biomechanical or anatomical axes.

Example 4 Patient-Adapted Implant Components and Guide Tools

This example describes designs and surgical implantation of knee implantcomponents and guide tools having certain patient-specific,patient-engineered, and/or non-traditional standard features. In thestudies described in this example, patient-adapted femoral, tibial, andpatellar implant components were designed and implanted for each ofthree cadaveric patients. In addition, corresponding resection cutstrategies were designed and performed. Moreover, several differentpatient-adapted guide tools were designed and used for the implantationprocedure.

The implant components and guide tools (also referred to as “jigs” or“iJigs”) for each patient were designed based on patient-specificCT-derived data from each patient. Specifically, data from CT images ofeach patient's knee was selected and imported into computer modelingsoftware. The software was used to generate a model of the biologicalstructures in the patient's knee and to design (e.g., using CADsoftware) a femoral implant component, a tibial implant component, andrelated guide tools. The design of the implant components and guidetools included manufacturing, for example, using CAM software andadditive and/or casting manufacturing techniques as described above. Inaddition, predetermined resection cuts to each patient's femur and tibiawere designed based on the patient's biology and in conjunction with thepatient-adapted features of the implant component. For example, theresection cuts and the corresponding component's bone-facing surfaceswere designed based on patient-specific data to substantially negativelymatch (e.g., in surface area, surface angle, and/or other feature).Then, surgery was performed on the cadaveric patient to perform thepredetermined (e.g., designed) resection cuts and to implant thecomponents designed for the particular patient. In addition, one or moreguide tools were designed and used for the procedure which also weredesigned to include patient-adapted features, for example, a bone-facingsurface that substantially negatively-matched the patient's anatomyand/or cutting guide slots or drilling guide holes that providedaccurate placement for the predetermined resection cuts and holes forthe particular patient.

4.1 Methods and Materials

Three surgical procedures were performed to implant femoral and tibialimplant components for three different cadaveric patients. Prior to eachsurgery, patient-adapted implant components (femoral and tibial implantcomponents) and guide tools were designed (including manufacturing) inconjunction with a resection cut design. Then, the guide tools were usedduring surgery to prepare the predetermined resection cuts and place theimplant components.

Femoral Implant Component

The patient-adapted femoral implant components each included six bonecuts. The bone cut design was designed in conjunction with correspondingresection cuts. FIGS. 103A and 103B, FIGS. 103C and 103D, and FIGS. 103Eand 103F, show the patient-adapted femoral implant and resection cuts,respectively, for each of the three patients. As exemplified in FIG.103A, the six bone cuts included an anterior bone cut 10310, medial10320M and lateral 10320L facets of a distal bone cut, medial 10330M andlateral 10330L facets of a posterior bone cut, an anterior chamfer bonecut 10340, medial 10350M and lateral 10350L facets of a first posteriorchamfer bone cut, and medial 10360M and lateral 10360L facets of asecond posterior chamfer bone cut. In addition, the femoral implantcomponent 10305 included a stepped (or “step”) cut 10370 between themedial facet 10320M and lateral facet 10320L of the distal bone cut inorder to provide enhanced preservation of distal medial bone stock. FIG.103C relating to the second patient and FIG. 103E relating to the thirdpatient include similar features as those numbered in FIG. 103A. As thefigures show, the non-coplanar distal bone cut facets, which can beconnected by a stepped cut, allow for independent and optionally minimumresection depths on the medial and lateral portions of an otherwisecontinuous bone cut (e.g., anterior bone cut, anterior chamfer bone cut,or distal bone cut).

Comparison between each of the three patient-adapted implant componentsand corresponding resection cuts shows various features of the implantcomponent that specifically match features of the resection cuts and/orof the patient's anatomy. For example, each implant component includes awidth, height, and condylar width that is patient-specific (i.e.,matches the patient's anatomy) or patient-engineered (i.e., derived frompatient-specific data to achieve one or more predetermined parameterthresholds, for example, an implant component peripheral margin thatdoes not overhang the cut surface of the bone and provides no more than1 mm or 0.5 mm or 0.3 mm exposed resection cut surface 10361).

Moreover, as shown by a comparison of the figures, the implant componentbone cuts for each patient was engineered to specifically-match theresection cuts for the patient (e.g., in cut and/or facet surface areas,angles, relative orientations, and/or other features). For example, asexemplified in FIG. 103B, the resection cuts included an anteriorresection cut 10310′, medial 10320M′ and lateral 10320L′ facets of adistal resection cut, medial 110330M′ and lateral 10330L′ facets of aposterior resection cut, an anterior chamfer resection cut 10340′,medial 10350M′ and lateral 10350L′ facets of a first posterior chamferresection cut, and medial 10360M′ and lateral 10360L′ facets of a secondposterior chamfer resection cut. In addition, the femoral implantcomponent included a stepped (or “step”) resection cut 10370′ betweenthe medial facet 10320M′ and lateral facet 10320L′ of the distalresection cut. FIG. 103D relating to the second patient and FIG. 103Frelating to the third patient include similar features as those numberedin FIG. 103B. As shown by the figures, the stepped cut 10320′ savessubstantial bone stock, for example, at the distal medial facet 10320M′in comparison to a distal medial facet cut having the same depth as thedistal lateral facet cut.

In addition, each patient-adapted femoral implant component included onthe joint-facing surface of each condyle a patient-specific J-curve thatsubstantially positively matched the J-curve of the particular patient'sfemur. Toward the anterior joint-facing surface, each implant componentincluded a trochlear groove profile that was patient-engineered to beoffset 2 mm laterally (e.g., relative to the particular patient'strochlear groove), and that was angled laterally. The first twopatients' implant components included a trochlear groove that engineeredto be angled laterally at approximately 3-5 degrees, while the thirdpatient's implant component included a trochlear groove that wasengineered to be angled laterally at approximately 5-7 degrees. Thetrochlear surface profile was designed to accommodate a dome-shaped(e.g., in profile) patellar implant component. On the bone-surface ofthe femoral implant component, two pegs 7 mm in diameter projected fromthe medial 10320M and lateral 10320L facets of the distal bone cut. Thereceiving peg holes in the patient's distal femur were prepared with an8 mm drill bit. Each bone cut and bone cut facet on the bone-facingsurface of the femoral implant included a cement cutout to hold cementapplied during the procedure.

Femoral Guide Tools

The guide tool designs were based on a tibial-cut-first technique. Forthe first two patients, a femoral all-in-one guide tool was designed toinclude guide slots and holes to perform all of the predetermined (e.g.,designed based on patient-specific data) femoral resection cuts and peghole placements. The all-in-one guide tools for each of the two patientsare shown in FIGS. 104A and 104B, respectively. As shown in the figures,the guide slots were numbered sequentially 1-11 to guide the surgeon inthe cutting steps and to maximize ease of use. The all-in-one guidetools 10402 also were prepared and provided to the surgeon in threedifferent thicknesses denoted by different letters 10404, which allowedthe surgeon to select the tool having the best fit, e.g., between thefemur in tibia with the knee in extension. Accordingly, this guide tool10402 aided the surgeon in assessing balance and implant fit, as well asproviding guide slots for all cuts and drill holes for the patient'sfemur. In addition, the bone-facing surface of each all-in-one guidetool was designed to be patient-specific (i.e., designed based onpatient-specific data to substantially match the correspondingbiological surface of the patient). Moreover, a comparison of the twopatient's guide tools, shown in FIGS. 104A and 104B, respectively, showsguide slots in different orientations from each other. These uniqueguide slot orientations are provided to establish the predeterminedresection cuts specifically designed in conjunction with apatient-adapted implant component for each patient based onpatient-specific data.

In addition, several guide tool attachments were designed and includedfor the for the all-in one guide tools 10402. For example, as shown inFIG. 105, a drill guide attachment 10502 was designed and included forattaching to the guide tool 10402 to extend the drilling surface.Moreover, as shown in FIGS. 106A, 106B, and 106C, various tooattachments 10602, 10604, 10606, 10608 were designed and included forattaching to the all-in-one guide tool to extend one or more cuttingsurfaces. For example, the attachment 10602 in FIG. 106A extends thecutting surface area for all cutting slots. The attachment 10604 in FIG.106B extends the surface area for the posterior resection cut slots10610 and for posterior chamfer resection cut slots 10612. Theattachment 10606 in FIG. 106B extends the surface area for the posteriorresection cut slots 10610. In addition, guide peg attachments 10608 weredesigned and included to provide additional surface area for theposterior chamfer resection cut slots 10612. As shown, the guide pegs10608 can be integrated with a guide attachment 10604 or can be usedindependently and, optionally, integrated with the guide tool 10402. Inaddition or as an alternative to extending a cutting surface, the guidepegs can be used to aid in securing the guide tool 10402 to thepatient's femur after peg holes are drilled into the patient's femur.

As an alternative to the all-in-one guide tool 10402, a set of threeguide tools also was designed and included for each of the first twopatients. FIGS. 107A, 107B, and 107C illustrate the set of three guidetools, which collectively supplied all of the guide slots and holes toperform each of the predetermined femoral resection cuts and peg holeplacements available in the single all-in-one guide tool 10402. This setof guide tools was included, for example, in case the all-in-one guidetool 10402 did not suit the needs of the surgeon. As with the all-in-oneguide tool 10402, each of the three guide tools in the set included oneor more patient-adapted features. As shown in FIG. 107A, the first guidetool 10780 in the set provided guide holes 10782 for drilling into thepatient's femur predetermined holes for receiving the femoral implantcomponent pegs. As shown in the figure, the guide tool 10780 is attachedto the patient's femoral bone 10784. The bone-facing surface of thefirst guide tool was designed to snap-fit to 3 mm of cartilage on thepatient's distal femur. As shown in FIG. 107B, a second balancing chipguide tool 10786 provided distal facet resection guide slots 10788, aslot to mark the termination of the distal lateral resection 10790(which can be used to establish the step cut between the distal lateraland medial resection facets), and a guide surface 10792 for making theposterior resection cut. As with the all-in-one guide tool, this tool10786 also can be used for balancing and assessing implant fit (e.g.,based on the fit of the guide tool between the femur and cut tibia inknee extension). As shown in FIG. 107C, a third chamfer cutting guidetool 10794 provided guide slots for the remaining predeterminedresection cuts. As shown, the cutting guide slots were identified withnumbers 1-6 to identify the order for performing the resection cuts.

For the third patient, a different set of femoral guide tools wasdesigned and included to perform the predetermined femoral resectioncuts and peg hole placements, as shown in FIGS. 108A through 108F. Asshown in FIG. 108A, a femoral trial guide tool 10830 was designed andincluded to guide the hole placement for the pegs on the subsequentlyused guide tools and on the femoral implant component. As shown, thisguide tool 10830 includes marks incorporated into its joint-facingsurface to indicate to the surgeon the locations representing theWhiteside Line 10832 and Epicondylar Axis 10834. As shown in FIG. 108B,the second guide tool, a balancer chip guide tool 10836, was designedand included for guiding independent distal medial 10838 and distallateral 10840 facet cuts, as well as the step cut 10842. Both thefemoral trial guide tool 10830 and the balancer chip guide tool 10836included a bone-facing surface derived from patient-specific data anddesigned to rest on 3 mm of cartilage atop the patient's femoral bonesurface. The balancer chip guide tool 10836 was provided in sixdifferent thicknesses to allow the surgeon to use the tool 10836 forligament balancing and assessment of the implant fit (e.g., by observingthe space or tightness of the tool 1636 positioned between the femur andcut tibia during flexion and extension). In addition, a spacing paddletool 10844, as shown in FIG. 108C, was designed and included forrepresenting the extra asymmetric lateral poly thickness when balancing.As shown in FIG. 108D, a chamfer cut guide tool 10846 was designed andincluded for guiding an anterior resection cut 10848, a anterior chamferresection cut 10850, and independent posterior medial 10852 andposterior lateral 10854 facet cuts. The a chamfer cut guide tool 10846was designed with pegs to fit into the previously prepared peg holes inthe patient's femur and with each cutting slot numbered for the order inwhich the cuts were to be performed. As shown in FIGS. 108E and 108F, apair of angled cut guides 10856, 10858 was designed and included tofacilitate the first and second posterior chamfer cuts. As shown, eachangled cut guide 10856, 10858 includes a first surface that matches thedistal resection surface and, optionally, includes pegs to fit into thepreviously prepared peg holes in the patient's femur. In the figures,the distal resection surface includes two non co-planar facets, whichfirst cut guide surface matches. In addition, each angled cut guide10856, 10858 also includes a second cutting guide surface angled at thepredetermined angle of the corresponding chamfer cut such that a cuttingtool placed against the surface cuts into the patient's bone at thepredetermined angle.

For the first two patients, and as shown in FIGS. 109A and 109B, ananterior profile guide tool 10902 also was designed and included tocompare the peak profile at the anterior portion of the femur in theinstalled implant as compared to the patient's native knee.

As discussed above, the trochlear area of the femoral implant componentwas patient-engineered (e.g., derived and/or optimized frompatient-specific data) to include a trochlear groove offset 2 mmlaterally and designed to accommodate a dome-shaped patellar implantcomponent. Accordingly, as shown in the figures, the anterior profile ofthe implant differs from the anterior profile of the patient's nativefemur, particularly in providing relief on the lateral side of theimplant relative to the patient's femur.

Tibial Guide Tools

Several guide tools for resectioning the tibia and/or placing the tibialimplant component were designed and included for each patient's surgery.For example, as shown in FIG. 110A, for each patient a cutting guidetool 11002 was designed and included for accurately resectioning theproximal tibia to a predetermined resection depth and angle (e.g., 2 mmbelow the lowest point of the medial plateau, with an AP slope of 5degrees and perpendicular to the mechanical axis). The anterior part ofthe tibial cutting guide tool 11004 was designed with a patient-specificbone-facing surface to substantially negatively-match the correspondinganterior portion of the patient's tibia when the medial edge of theguide was aligned to the medial one-third of the patient's tibialtubercle 11006. The proximal part 11008 of the tibial cutting guide tool11002 was designed to rest on an estimated 2 mm thick cartilage layeratop the patient's proximal tibia that was identified frompatient-specific data. For the first two patients, an alternate tibialcutting guide tool 11010 shown in FIG. 110B also was designed andincluded. The alternate tibial cutting guide tool 11010 included thesame features of tibial cutting guide 11002 except that the proximalpart 11008 of the alternate tibial guide tool 11010 was designed to restdirectly on the bone surface of the patient's proximal tibia wasidentified from patient-specific data, rather than on a cartilagesurface.

The tibial cutting guide tools 11002, 11010 were designed to include adovetail mating feature 11012 that was attachable to a tibial alignmentguide tool 11014 and down rod 11016 to visually check the alignment ofthe guide tools with the patient's mechanical axis. FIG. 110C depictsthe tibial alignment guide tool 11014 and down rod 11016 attached viathe dovetail connection to a tibial cutting guide tool 11002, 11010 toconfirm prior to cutting the alignment of the cutting guide tool 11002,11010 with respect to the patient's mechanical axis. The tibialalignment guide tool 11014 included a complementary dovetail matingfeature to attach to the tibial cutting guide tools.

For the third patient and, as shown in FIG. 110D, the tibial cuttingguide tool 11002 included two small holes on the anterior portion of thetool through which the patient's femur was marked with a pen or otherinstrument. The two markings on the surface of the cut tibia, as shownin FIG. 110D, served as landmarks for placement of subsequent tools.

For each patient, tibial keel preparation guide tools were designed andincluded to facilitate preparation of the holes and slots into theproximal, resected tibial surface and thereby ensure proper placement ofthe tibial tray keel and tibial implant component generally. A differentset of tibial keel preparation guides were used for each of the threepatients. For the first patient and as shown in FIG. 111A, a tibial keelprep guide tool 11108 was designed and included. To help ensure properplacement, the perimeter (except for the handle portion) of the tool11108 was designed to substantially match the perimeter of the tibialtray implant component, which itself was patient-adapted tosubstantially match the perimeter of the patient's resected tibialsurface. Accordingly, the proper placement of the tibial prep guide tool11108 could be discerned by the surgeon by aligning the perimeter of thetibial prep guide tool 1608 with the perimeter of the patient's resectedtibial surface. In addition, the medial edge of the handle 11110 of thetibial prep guide tool 11108 was designed to align with the medial ⅓ ofthe tibial tubercle 11006 to further ensure proper tibial implantrotational alignment. The central hole was drilled using a 0.5 inchdiameter drill bit. As shown in FIG. 111B, a set of tibial keel prepinsert guides 11112, 11112′, 11112″ was designed to mate with the tibialprep guide 11108 once the central hole was drilled. The tibial keep prepinsert guides 11112, 11112′, 11112″ allow for controlled intra-operativetibial implant rotational alignment according to predetermined amountsof rotation. For example, as indicated in the figure, the set of tibialprep guides included a first tibial keel prep insert guide 1612 thatprovided 0 degrees of rotation, a second tibial keel prep insert guide11112′ that provided 5 degrees of rotation, and a third tibial keel prepinsert guide 11112″ that provided 10 degrees of rotation. After thesurgeon selected the tibial keel prep guide that desired predeterminedamount of rotation, slots were created using the guide holes in theselected tibial keep prep guide to drill multiple angled holes (e.g.,six holes corresponding to the six guide holes in the tibial keep prepguide) using a 4 mm drill bit. Once the 4 mm holes were drilled into thepatient's resected proximal tibial surface, an osteotome was used tocreate a rectangular slot for the keels of the tibial tray implantcomponent.

For the second patient and as shown in FIG. 112, a tibial keel prepguide tool 1660 was designed and included for establishing the keel slotin the patient's resected proximal tibial surface. Similar to the tibialkeel prep guide tool 11108 for the first patient, the tibial keel prepguide tool 11208 for the second patient included a perimeter (except forthe handle portion) designed to substantially match the perimeter of thetibial tray implant component, which itself was patient-adapted tosubstantially match the perimeter of the patient's resected tibialsurface. However, for the second patient an optional drill guide 11210and a keel saw guide 11212 also were designed and included. The drillguide was available to be inserted into the central opening of thetibial keel prep guide tool 11208 to provide an accurately placedcentral hole. In addition, once the central hole was established, thekeel saw guide 11212 was available to be inserted to provide a narrowchannel for sawing an accurately slot for receiving the keel of thetibial implant component.

As shown in FIGS. 113A and 113B, the tibial keel prep guide tool 11308for the third patient incorporated features from the first patient'stibial keel prep guide tool 11108 and insert guide tool 11112. However,unlike the tibial keel prep guide tools for the first two patients, thistool 11308 did not include a handle. In certain embodiments, more thanone such tool 11308 can be included having different orientations ofholes to provide different degrees of rotation for the keel and tibialtray. Similar to the tibial keel prep guide tools for the first twopatients, this tool 11308 also included a perimeter designed tosubstantially match the perimeter of the tibial tray implant component,which itself was patient-adapted to substantially match the perimeter ofthe patient's resected tibial surface. As shown in the figures, an arrowwas located on the proximal surface of the tool 11308 that indicatedalignment to the medial ⅓ of the tibia tubercle for proper tibialimplant rotational alignment (which itself had been marked, as describedabove). The central hole was drilled using an 9/16″ drill bit and thekeel holes were drilled using a ⅛″ drill bit, before cutting betweenthem with an osteotome to establish the keel slots.

As shown in FIG. 114A, a set of tibial trial spacers was designed andincluded for the second and third patients. Specifically, for the secondpatient, two medial trial spacers were provided in thicknesses of 6 mmand 8 mm, respectively (second patient) or 8 mm and 10 mm, respectively(third patient) and three lateral trial spacers were provided inthicknesses of 9 mm, 10 mm, and 11 mm, respectively (second patient) or10 mm, 11 mm, and 12 mm, respectively (third patient). The spacers wereused to assess balance and fit, for example, to assess the tightness andbalance of the joint with the spacer in place to represent tibialimplant thickness between the cut tibia and femur (and optionally othercomponents in place representing femoral thickness) during flexion andextension of the knee.

For each patient and as shown in FIG. 114B, a set of tibial implantcomponent trial inserts was designed and included for each patient inorder for the surgeon to assess the appropriate thicknesses to use formedial and lateral tibial implant component inserts for properlybalancing the patient's knee joint. As shown in the figure, two medialtrial inserts 111408, 11408′ and three lateral trial inserts 11420,11420′, 11420″ were designed and included. The two medial trial insertshad thicknesses of 6 mm and 8 mm, respectively, and the lateral trialinserts had thicknesses of 8.5 mm, 9.5 and 10.5 mm, respectively (firstpatient) or 9 mm, 10 mm, and 11 mm, respectively (second patient) or 8mm, 9 mm, and 10 mm, respectively (third patient). After assessing thetrial inserts and deciding on an appropriate medial and lateral insertthickness for balancing, the surgeon positioned the tibial implant trayand inserts having the appropriate thicknesses medially and laterally.

Tibial Implant Components

As shown in FIGS. 115A and 115B, the tibial implant components that weredesigned and included for each patient comprised a tibial tray 11522 anda set of tibial inserts 11524, 11526. The tibial tray 11522 was designedto include a patient-specific perimeter 11528 that substantially matchedthe perimeter of the patient's resected proximal tibial surface. Inaddition, the tibial tray 11522 was designed to include a 11 mm×35 mm(first and second patients) or a 13 mm×40 mm (third patient) centralstem and 3.5 mm wide keels that were angled posteriorly 5 degrees on themedial and 15° on the lateral side and match the orientation of theholes created by the tibial keel prep guide 11512′. The tibial inserts11524, 11526 were designed and provided to have the same thicknesses asthe tibial trial inserts 11408, 11420 described above. As shown in thefigure, the tibial trial inserts 11524, 11526 were designed to have alocking fit onto the tibial tray joint-facing surface 11530.

The perimeters of the trial spacers (except for the handle portion),tibial implant component trial inserts, and tibial inserts were designedto substantially match the perimeter of the tibial tray implantcomponent, which itself was patient-adapted to substantially match theperimeter of the patient's resected tibial surface.

Patellar guide tool and implant components

In addition to the patient-adapted femoral and tibial implant componentsthat were designed and included, a patient-adapted patellar implantcomponent and related guide tools also were designed and included forthe third patient's surgery. For example, as shown in FIG. 116A, a setof patella sizers was designed and included to assess the diameter ofthe patella. As shown in FIG. 116B, a patellar cutting tool was designedand included to cut the patella to a predetermined depth of resection.In addition, various patella implant trials also were designed (e.g.,using 3D print manufacturing) and included. As shown in FIG. 116C, theimplant trials included diameters of 32 mm, 35 mm, 38 mm, and 41 mm,respectively. As shown in FIG. 116D, a patellar implant of 41 mm wasselected and implanted for the third patient.

4.2 Results and Discussion

The patient-adapted implant components were successfully implanted usingthe resection cuts and patient-adapted guide tools that werespecifically designed for each cadaveric patient based on particularpatient data (e.g., image data). Specifically, the tibial cut guidetools showed good fit with the patient's tibial plateau. The alignmentguide tool and the drop down rod helped to confirm proper tibialalignment of the cut guide tool prior to resectioning for each patient.The different guide tools used to prepare the stem holes and keel slotsin the proximal, resected surface of each patient's femur were found touseful. The tibial guide tools designed to include a patient-derivedperimeter were found to fit well with the perimeter of each patient'sresected tibia. The matching perimeter was helpful in properly aligningthe cut tools to establish the predetermined resection cuts and/or forbalancing. Regarding the patient-adapted tibial implant components, thetibial tray perimeter was shown to have a perimeter profile thatsubstantially matched the perimeter of the patient's resected proximaltibial surface, with no excessive overhang or underhang. The tibialtrial inserts were helpful in selecting the proper medial and lateraltibial inserts for balancing and fit. The tibial inserts were easily fitinto the locking mechanism of the tibial tray. Overall, thepredetermined tibial resection cuts, patient-adapted tibial guide tools,and patient-adapted tibial implant components provided a well-fit andaligned implant component.

On the femoral side, the single all-in-one guide tool used with thefirst two patients was found to have a patient-specific bone-facingsurface that fit well to each patient's biological surface. Theposterior and distal thickness of the tool was useful to assess balanceand tightness/looseness of the joint. The set of femoral guide toolsused to resect the third patient's femur were found to be useful formaking the predetermined resection cuts. Regarding the patient-adaptedfemoral implant components, once in place the component for each patientwas shown to have good coverage of the resected surfaces of thepatient's femur and proper articulation with the tibial component.

FIGS. 117A through 117D show exemplary steps in the surgical proceduresdescribed above. In particular, FIG. 117A shows the use of a the tibialcut guide tool attached to an alignment guide tool for guiding thepredetermined resection cut to the proximal tibia (for patient #2). FIG.117B shows the placement of a tibial tray having a patient-adaptedperimeter (for patient #2). FIG. 117C shows the use of an all-in-oneguide tool for guiding the predetermined resection cuts to the femur(for patient #2). FIG. 117D shows a fluoroscopic image of the implantedfemoral and tibial implant components (for patient #3).

Example 5 Implant Component with Curvilinear Bone Cuts

This example illustrates an implant component having both straight andcurvilinear bone cuts on its bone-facing surface. Specifically, afemoral implant is designed to include 3 mm curvilinear cut depths andcorresponding implant thicknesses along the distal portion of eachcondyle. The cut depth and implant thickness along each condyle aredesigned independently of the other condyle. In addition, jigs forperforming the curvilinear cuts to the articular bone surface aredescribed.

Using a computer model generated from patient-specific data, posteriorand anterior resection cut lines are created in the model, as shown inFIGS. 118A and 118B. To design the curvilinear bone cut linecorresponding to the resection cut on the medial condyle, a medial splitline is identified on the condyle, as shown in FIG. 119A, and then a 3mm deep cut line is generated to follow the split line, as shown in FIG.119B. The resulting virtual curvilinear cut is shown in FIG. 119C. Thesame steps are performed independently for the lateral condyle, as shownin FIGS. 120A to 120C.

The resulting resection cut model, as shown in FIG. 121A establishespredetermined resection cuts for the surgical procedure and it also canbe used to engineer the bone-facing surface of the correspondingpatient-specific implant component, as shown in FIGS. 121B and 121C.Specifically, the inner, bone-facing surface of the implant componentcan be designed and engineered to substantially negatively-match theresection cut surface on the model. Optionally, and as shown in thefigures, the outer, joint-facing surface of the implant also can includeone or more patient-specific features.

The resulting cut model also can be used to design one or more cuttingjigs that are fitted to the bone to guide the bone cutting procedure.For example, FIG. 122A shows a model of a bone along with a jig thatallows preparation of predetermined resection holes and, optionally,resection cuts surfaces to match the predetermined resection cutsspecific to a patient's particular anatomy. FIGS. 122B and 122C show analternative set of jigs that can be used with a router-type saw.Specifically, a router-type bit can fit into the central channel of thejig shown in FIG. 122B to cut along the channel to a specific depth, forexample, 3 mm. Then, as shown in FIG. 122C, a second jig having twochannels that circumvent the channel of the first jig can be applied.The router-type bit can fit into these two channels to cut medial andlateral to the first channel to the same depth, for example, 3 mm.

FIG. 123A shows a model of the prepared bone following jig-guided bonecuts. FIG. 123B shows the model of FIG. 123A with a two-piecepatient-specific implant component designed with an inner bone-facingsurface that substantially negatively-matches the patient's resectedbone surface.

Example 6 Implant and Implant Design with Resurfacing

This example illustrates (a) an implant component and design having aresurfaced portion and a bone cut portion and (b) an implant and implantdesign having a resurfaced surface with no bone cuts.

Using a patient-specific model (e.g., CAD model) generated frompatient-specific data, a femoral implant is designed to include asingle, posterior cut on its inner, bone-facing surface, as shown inFIG. 8A above and in FIGS. 124A and 124B. The remaining portions of theinner, bone-facing surface of the implant are designed to substantiallynegatively-match the patient's uncut articular bone surface that theimplant component engages. Optionally, the outer, joint-facing surfaceof the implant also can include one or more patient-specific features.As shown in the figures, the patient-specific implant component with asingle bone cut is prepared as two pieces or components, which allowsfor fitting the curved anterior portion of the implant component 12400around the anterior portion 12402 of the femur.

The femoral implant design shown in FIGS. 125A and 125B and thecorresponding implant shown in FIG. 125C also uses a two-piece ortwo-component design, in part to allow for fitting the curved anteriorportion of the implant 12400 around the anterior portion 12402 of thefemur. Specifically, using a patient-specific model generated frompatient-specific data, a femoral implant was designed to include no bonecuts on its inner, bone-facing surface. Instead, the inner, bone-facingsurface of the implant was designed to substantially negatively-matchthe uncut articular bone surface that the implant component engages.Optionally, the outer, joint-facing surface of the implant also can bedesigned and engineered to include one or more patient-specificfeatures.

Example 7 A Femoral Component Device with Enhanced Articular Surface

This example illustrates exemplary implant components having enhancedarticular surfaces (i.e., joint-facing surfaces). FIG. 126A is a frontschematic view of engaging portions of a single compartment (e.g., asingle condyle) of a knee implant 12601.

FIG. 126B is a cross-sectional schematic view in the coronal plane of afemoral component 12602 of the implant 12601 of FIG. 126A. Withreference to FIG. 126A and FIG. 126B, this exemplary embodiment of apatient-specific implant component 12601 includes a femoral component12602 and a tibial tray component 12603, and it is designed based onpatient-specific data. An inner, bone-facing surface 12604 of thefemoral component 12602 conforms to the corresponding surface of thefemoral condyle. Alternatively, it can conform to one or more optimizedbone cuts on the femoral condyle. However, the outer, articular surface12605 of the femoral component 12602 is enhanced to incorporate a smoothsurface having an approximately constant radius in the coronal plane.The corresponding articular surface 12607 of the tibial tray 12603 has asurface contour in the coronal plane that is engineered based on thecoronal plane to the outer articular surface 12605 of the femoralcomponent 12602. In this embodiment, the articular surface 12607 has aradius that is five times the radius of the outer articular surface12605. In certain embodiments, the articular surface 50 of the femoralcomponent 12602 includes a sagittal curvature that matches the patient'sexisting or healthy sagittal radius.

FIGS. 126C to 126F show cross-sectional schematic views in the coronalplane of respective alternate embodiments of a femoral component.

The design of implant component 12601 has several advantages. First, thedesign of articular surface 12605 allows the thickness of femoralcomponent to be better controlled as desired. For example, referring toFIG. 126C, if a curve of an articular surface 12608 of a femoralcomponent 12609 is too large, the thickness of the femoral component maybe too thick along a centerline 12610 of the implant, thereby requiringan excessive amount of bone to be removed when the implant is placed onthe femoral condyle. On the other hand, referring to FIG. 126D, if thesame curve 12608 is applied to a device having an appropriate centerlinethickness 110, the margins or sidewalls 12612, 12613 of the device maybe too thin to provide proper structural support. Similarly, referringto FIG. 126E, if the curve of the outer articular surface 12612 of afemoral component 12613 is too flat, the device does not exhibit thetapering from a centerline 12614 to the margins or sidewalls 12615,12616 of the device and may not function well.

Referring again to FIGS. 126A and 126B, a second advantage of implantcomponent 10 over certain other embodiments of patient-specific devicesis that the smooth articular surface 50 can provide enhanced kinematicsas compared to a true representation of the surface of the patient'sfemoral condyle.

For example, referring also to FIG. 126F, one method of makingpatient-specific implants is to use a simple offset, in which a femoralcomponent 12617 is designed using a standard offset from each point ofthe modeled surface of the patient's femoral condyle. Using such adesign, the thickness of the device remains essentially constant, and anouter surface 12618 essentially positively-matches or conforms to theunderlying inner femoral-facing surface 12619, as well as the modeledsurface of the femoral condyle on which it is based. While this providesa truly patient-matched joint-facing surface, it is not necessarilyoptimal for the kinematics of the resulting implant, due to, forexample, rough areas that may produce higher, more localized loading ofthe implant. By using a smooth surface with an essentiallypre-determined shape, the loading of the implant can be better managedand distributed, thereby reducing the wear on the tibial tray component12603.

A third advantage, which also is related to the loading and overallkinematics of the implant, is in the negative-matching of the tibialarticular surface 12607 to the femoral articular surface 12605 in thecoronal plane. By providing a radius that is predetermined, for example,five times the radius of the femoral articular surface 50 at itscenterline in the present embodiment, the loading of the articularsurfaces can be further distributed. Thus, the overall function andmovement of the implant is improved, as is the wear on the tibialbearing surface, which can include polyethylene material. While theembodiment described above uses a ratio of five times the radius of theouter surface at its centerline (note that the radius of the outersurface may be slightly different at other locations of the outersurface 50 away from the centerline), other embodiments are possible,including an outer tibial surface that, in the coronal plane, is basedon other ratios of curvature, other curvatures, other functions orcombinations of curves and/or functions at various points. Additionally,while the embodiments shown in FIG. 126C through FIG. 126F are notconsidered to be optimal designs generally, they are embodiments thatcan be generated using automated systems and may have preferablecharacteristics in some instances.

Example 8 A Patient-Specific Engineered Trochlea Design

This example describes a patient-specific trochlea design that isoptimized for proper kinematics of the patella-femoral (“PF”) joint.

8.1 Method

FIGS. 127A to 127F show an exemplary design of a knee implant, includinga femoral component and a patella component, with a material cutawayregion highlighted (darker) in certain figures. The placement of thepatella and material removal was as follows: As shown in FIG. 127A, theflat bone-bearing surface of the patella 12700, was made parallel to theepicondylar axis 12710 in the coronal view. As shown in FIG. 127B, thecenter plane of the patella implant was made collinear with theepicondylar axis 12720. This allows for general positioning at the peakarea of the trochlea. As shown in FIG. 127C, in this position themedial-lateral center or sulcus of the trochlea is identified 12730, andthe patella implant component is brought down, so the lowest points arecoincident 12740. As shown in FIGS. 127D through 127F, the patellaprofile is swept along the sagittal curve of the trochlear region 12750.

8.2 Results and Discussion

This exemplary implant design uses a patient-specific sagittal curvatureand an engineered coronal curvature to allow the patella component totrack properly in the trochlear groove. This exemplary implant designfor the femoral component and a patella component can allow variousadvantages including a reduction of lateral overstuffing of the P-Fjoint and a post-operative patella tracking that is normal or close tothe patient's pre-operative and/or pre-disease state. In certainembodiments, the lateral peak can be retained, which may minimizedislocation events. In certain embodiments, the patella implantbone-bearing surface can be or appear to be approximately parallel tothe osteochondral junction of the native patella.

Example 9 Exemplary Method for Virtually Aligning a Patient's LowerExtremity

From a three-dimensional perspective, the lower extremity of the bodyideally functions within a single plane known as the mediananterior-posterior plane (MAP-plane) throughout the flexion-extensionarc. In order to accomplish this, the femoral head, the mechanical axisof the femur, the patellar groove, the intercondylar notch, the patellararticular crest, the tibia and the ankle remain within the MAP-planeduring the flexion-extension movement. During movement, the tibiarotates as the knee flexes and extends in the epicondylar axis, which isperpendicular to the MAP-plane.

As shown in FIG. 128, the mechanical axis of a patient's lower extremitycan be defined by the center of hip 12802 (located at the head 12830 ofthe femur 12832), the center of the knee 12804 (located at the notchwhere the intercondylar tubercle 12834 of the tibia 12836 meet thefemur) and the center of the ankle 12806. In the figure, the long axisof the tibia 12836 is collinear with the mechanical axis of the lowerextremity 12810. The anatomic axis 12820 aligns 5-7 degrees offset θfrom the mechanical axis in the valgus, or outward, direction. A varietyof image slices can be taken at each joint, for example, at one or moreof the knee joint 12850-12850 n, the hip joint 12852-12852 n, and theankle joint, to determine the mechanical centerpoint for each joint.

In certain preferred embodiments, anatomic reference points are used tovirtually determine a patient's misalignment and the proper mechanicalaxis of his or her lower extremity. Based on the difference between thepatient's misalignment and the proper mechanical axis, a knee implantand implant procedure can be virtually designed to include implantand/or resection cut features that substantially realign the patient'slimb to have a proper mechanical axis. The implant design process caninclude manufacturing the implant (e.g., using CAM software) and,optionally, the implant can be surgically implanted into the patientaccording to the virtually designed procedure.

In certain embodiments, a patient's proper mechanical axis of the lowerextremity, and the extent of misalignment of the extremity, is virtuallydetermined using an appropriate computer-aided design software program,such as SolidWorks software (Dassault Systemes SolidWorks Corp., 300Baker Avenue, Concord, Mass. 01742). Using the software,patient-specific information, for example, a collection of anatomicreference points, is used to generate a virtual model that includes thepatient's knee joint.

The virtual model also can include reference points from the hip and/orankle joints. Using the virtual model, a user can determine virtuallythe misalignment of and mechanical axis of the patient's lower extremityby determining in the model the patient's tibial mechanical axis,femoral mechanical axis, and one or more planes from each axis. Forexample, the patient's tibial mechanical axis can be determinedvirtually in the model as a line connecting the center of the patient'sankle and the center of the patient's tibia. The patient's femoralmechanical axis can be determined virtually in the model as a lineconnecting the center of the patient's hip and the center of thepatient's distal femur. The center of the patient's ankle, tibia, hip,and/or distal femur can be determined based on the patient-specificanatomic reference points or landmarks used to generate the virtualmodel.

Then, the user can align virtually the lower extremity by collinearlyaligning the tibial and femoral mechanical axes. This collinearalignment can be achieved by adjusting the angle of the intersectingaxes at the knee joint to be zero. The axes can be aligned axially byaligning one or more planes common to both axes, such as the sagittal orcoronal planes.

FIGS. 129A to 129C each illustrate a model showing the existingmisalignment of a patient's lower extremity (dark and solid line) andthe virtual alignment (light and dashed line) determined using themodel.

Exemplary methods for determining the tibial mechanical axis, thefemoral mechanical axis, and the sagittal and coronal planes for eachaxis are described in more detail in the following subsections.

9.1 Methods for Determining Tibial Mechanical Axis and its Sagittal andCoronal Planes

In certain embodiments, the tibial mechanical axis and the tibialsagittal and coronal planes are determined virtually using a model thatincludes reference points from a patient's knee and ankle joints, asfollows:

9.1.1 Tibial Mechanical Axis

1a. Axial plane of the ankle. As shown in FIG. 130A, an axial plane atthe ankle is identified using three or more points at the inferiorarticular surface of the tibia. The three or more points are selectedfrom the same or closely similar elevation(s) on the inferior articularsurface of the tibia. This optional step can be used to establish aninitial plane of reference for subsequent virtual determinations.

1b. Distal point of the tibial mechanical axis. The distal point of thepatient's tibial mechanical axis can be defined as the center of theanlde. As shown in FIG. 130B, the center of the ankle can be determinedvirtually by connecting a line from the medial to the lateral malleoliand marking 4 percent medial from the center of the line. For example,if the distance between the malleoli is 100, then the center of the lineis at 50 and the center of the ankle is 4 percent medial from the centerof the line or, in other words, at 46 from the medial malleoli and 54from the lateral malleoli.

1c. Proximal point of the tibial mechanical axis. The proximal point ofthe tibial mechanical axis can be determined virtually as the posterioraspect of the ACL insertion point, as shown in FIG. 130C.

1d. Tibial mechanical axis. The tibial mechanical axis can be determinedvirtually as the line connecting the distal and the proximal points ofthe tibial mechanical axis, as shown in FIG. 130D.

9.1.2 Sagittal or A-P Plane of the Tibia

2a. Tibial axis perpendicular plane (“TAPP”). The TAPP can be determinedvirtually as the plane perpendicular to the tibial mechanical axis lineand including the proximal point of the tibial mechanical axis, as shownin FIG. 131A. This optional step can be used to establish a plane ofreference for subsequent virtual determinations. The TAPP, optionallytilted in an A-P orientation, also can be used to determine the tibialcut line.

2b. A-P line of the tibia—derived from Cobb method. The A-P line of thetibia can be determined virtually based on method derived from Cobb etal. (2008) “The anatomical tibial axis: reliable rotational orientationin knee replacement” J Bone Joint Surg Br. 90(8):1032-8. Specifically,the A-P line of the tibia can be determined virtually as the lineperpendicular to the line connecting the diametric centers of thelateral and medial condyles of the tibia. For example, as shown in FIGS.131B and 131C, a best-fit circle can be sketched to determine thediametric center of the lateral condyle (i.e., the lateral plateau ofthe tibia). In addition, a best-fit circle can be sketched to determinethe diametric center of the medial condyle (i.e., the medial plateau ofthe tibia).

In certain embodiments, one or both of the circles can be sketched tobest fit the corresponding condyle(s) at the superior articular surfaceof the tibia. Alternatively, one or both of the circles can be sketchedto best fit a portion of the wear pattern at the superior articularsurface of the tibia. Still yet, one or both of the circles can besketched to best fit the condyle(s) at a certain distance distal to thesuperior articular surface of the tibia. For example, the circle for themedial condyle can be sketched to best fit the medial condyle at 10 mm,15 mm, 20 mm, 25 mm or more below, or distal to, the superior articularsurface of the tibia; and then the circle can be adjusted proximally tolie on the plane of the superior articular surface of the tibia.

Then, as shown in FIG. 131D, A-P line of the tibia is determinedvirtually as the line perpendicular to, and including the midpoint of,the line connecting the diametric centers of the lateral and medialcondyles of the tibia. If the midpoint of the line connecting thediametric centers of the lateral and medial condyles is not in the samelocation as the proximal point of the tibial mechanical axis, then theA-P line can be shifted away from the midpoint to include the proximalpoint of the tibial mechanical axis while remaining perpendicular to theline connecting the diametric centers of the lateral and medialcondyles.

A-P line of the tibia—derived from Agaki method. An alternative methodfor determining virtually the A-P line can be derived from otherpublished methods, such as Agaki (2004) “An Anteroposterior Axis of theTibia for Total Knee Arthroplasty,” Clin Orthop 420: 213-219.

2c. Sagittal or A-P plane of the tibia. As shown in FIG. 131E, thesagittal or A-P plane of the tibia can be determined virtually as theplane including both the A-P line of the tibia and the tibial mechanicalaxis line. The sagittal or A-P plane also is perpendicular to the TAPP.

9.1.3 Coronal or Medial-Lateral (“M-L”) Plane of the Tibia

As shown in FIG. 131F, the coronal or M-L plane of the tibia can bedetermined virtually as the plane perpendicular to the A-P plane (orperpendicular to the A-P line) of the tibia and including the tibialmechanical axis line. The coronal or M-L plane also is perpendicular tothe TAPP.

9.2 Methods for Determining Femoral Mechanical Axis and its Sagittal andCoronal Planes

In certain embodiments, the femoral mechanical axis and the femoralsagittal and coronal planes are determined virtually using a model thatincludes reference points from a patient's knee and hip joints, asfollows:

9.2.1 Femoral Mechanical Axis

1a. Axial plane of the femur. As shown in FIG. 132A, an axial plane ofthe femur is selected virtually using three or more points within thespherical femoral head that substantially lie in the same axial plane.This optional step can be used to establish an initial plane ofreference for subsequent virtual determinations.

1b. Proximal point of the femoral mechanical axis. As shown in FIG.132B, the proximal point of the patient's femoral mechanical axis can bedetermined virtually as the center of the spherical femoral head.

1c. Distal point of the femoral mechanical axis. As shown in FIG. 132C,the distal point of the femoral mechanical axis is determined virtuallyas the point at the posterior aspect of the femoral trochlear notch orsulcus.

1d. Femoral mechanical axis. The femoral mechanical axis can bedetermined virtually as the line connecting the distal and the proximalpoints of the femoral mechanical axis, as shown in FIG. 132D.

9.2.2 Sagittal or A-P Plane of the Femur

2a. Femoral mechanical axis perpendicular plane (FMAPP). The FMAPP canbe determined virtually as a plane perpendicular to the femoralmechanical axis line and including the distal point of the femoralmechanical axis, as shown in FIG. 133A. This optional step can be usedto establish a plane of reference for subsequent virtual determinations.In certain embodiments of implant procedures that require femoral cuts,the distal femoral cut is applied at the FMAPP.

2b. A-P line of the femur—derived from Whiteside's line. As shown inFIG. 133B, the A-P line of the femur can be determined virtually as theline perpendicular to the epicondylar line and passing through distalpoint of the femoral mechanical axis. The epicondylar line is the lineconnecting medial and lateral epicondyles (furthest out points).

2c. Sagittal or A-P plane of the femur. As shown in FIG. 133C, thesagittal or A-P plane of the femur can be determined virtually as theplane including both the A-P line of the femur (derived from theWhiteside's line) and the femoral mechanical axis line. The sagittal orA-P plane also is perpendicular to the plane perpendicular to thefemoral axis.

9.2.3 Coronal or Medial-Lateral (“M-L”) Plane of the Femur

As shown in FIG. 133D, the coronal or M-L plane of the femur can bedetermined virtually as the plane perpendicular to the A-P plane (orperpendicular to the A-P line) of the femur and including the femoralmechanical axis line. The coronal or M-L plane also is perpendicular tothe plane perpendicular to the femoral axis.

After determining virtually the tibial and femoral mechanical axis, andtheir sagittal and coronal planes, the lower extremity can be alignedvirtually by adjusting the angle of the intersecting mechanical axes atthe knee joint to be zero. The axes can be aligned axially by aligningone or both of the sagittal or coronal planes from each axis, as shownin FIGS. 134A and 134B, respectively. FIGS. 135A and 135B show a modelbefore and after virtual alignment as it appears in axial view lookingdistally from a section of the femoral head, to a section of the distalfemur, and on to a section of the tibia. Similarly, FIGS. 135C and 135Dshow a model before and after virtual alignment as it appears in axialview looking proximally from a section of the distal tibia, to a sectionof the distal femur, and in FIG. 135C, on to a section of the femoralhead. FIGS. 135E to 135G show a model before and after virtual alignment(FIGS. 135E and 135G), and an overlay of both before and after virtualalignment (FIG. 135F).

Various features of the patient-adapted implant components, includingbone cut angles, bone cut slopes, bone cut number, implant thickness inone or more portions, joint facing curvature, implant componentthickness, and other features, can be selected and/or designed, at leastin part, to optimize the parameter of deformity correction and/or limbalignment, for example, using the virtual alignment method describedherein. Optionally, one or more other parameters can simultaneously befactored into the selection and/or design of implant component features.For example, in addition to limb alignment, the implant componentfeatures also can be selected or designed meet one or more of thefollowing parameters: (1) preserving, restoring, or enhancing thepatient's joint kinematics; (2) deformity correction; (3) maximizingpreservation of bone cartilage, or ligaments (e.g., resulting from theresection); (4) maximizing preservation and/or optimization of otherfeatures of the patient's anatomy, such as trochlea and trochlear shape;(5) restoration or optimization of joint-line location and/or joint gapwidth, and (6) preservation, restoration, or enhancement of other targetfeatures.

Example 10 Finite Element Analysis

This example illustrates an exemplary finite element analysis (“FEA”)that can be conducted on a device component of some embodiments as oneparameter in the optimization of patient-specific features of theimplant. Specifically, this example describes FEA conducted on threevariations of a femoral implant component.

10.1 Methods

This analysis investigates the effect of interference fit and loadingscenarios on three different large knee femoral implant designs,including, as shown in FIGS. 136A to 136C, respectively, a componentwith six bone cuts and a perpendicular distal bone cut (“Perp 6-Cuts”);a component with five bone cuts and a perpendicular distal bone cut(“Perp 5-Cuts”); and a component with six bone cuts and flexed bone cuts(“Flexed 6-Cuts”). The three femoral implant component geometries testedrepresented implants for the largest expected anatomy. FIGS. 137A to137C each show a traditional implant component overlaid with each of thethree tested implant components. In addition, FIG. 138 shows atraditional component overlaid with the 6-Cuts implant component in anoverlaid position that respects the actual implant placements based onmovement of the joint-line. FIG. 139 shows the joint-facing surface ofthe 6-Cuts implant component positioned on a femur having sixcorresponding resection cuts.

Target results of the FEA analysis included identification of maximumprinciple stresses and displacements. For a general reference onconducting FEA on knee implant components, see “Initial fixation of afemoral knee component: an in vitro and finite element study,” Int. J.Experimental and Computational Biomechanics, Vol 1, No. 1, 2009.

FIG. 140 shows set-up information for the testing. For initial runs ofthe three variations, the models of the femur were setup with 0.35degrees interference fit angles on the Anterior Shield (A, FIG. 141A),and upper most medial and lateral condyle (B and C, FIG. 141B) surfaces.This angle was set by running iterative analyses until a Max PrincipalStress of roughly 240 MPa (the fatigue endurance limit of CoCr) wasachieved. Secondary analysis runs were performed with no interferencefit on the three Femoral Implant geometries.

All contact surfaces between the implant and femur (D, FIG. 141C) wereset up as frictional (0.5 coefficient of friction based on the generalreference described above), and the surfaces between the implant andcondyle support plates (E, FIG. 141C) were frictionless.

For all cases the top face of the femur (F, FIG. 141D) was fully fixed.The bottom faces of the condyle support plates (G and H, FIG. 141E) wereeither fixed in all directions or, when the load was applied, allowed tomove along the femoral axis only (Z direction shown on visiblecoordinate system).

Loads of 1601 N (360 lbs.) to the lateral condyle support plate and 2402N (540 lbs.) to the medial condyle support plate were applied in thedirection of the Femoral Axis (Z axis shown, FIG. 141F). A balance wasstruck to align model performance with the different contact areas andresults. The overall mesh is shown in FIG. 141G. The mesh of the implantcomponent was refined for best results in the high stress areas (FIG.141H).

10.2 Results and Discussion

The three different large knee femoral implant component geometries thatwere assessed were sized to correspond to large anatomical knees. Theresults for Interference No Load, Interference Plus Load, and NoInterference Plus Load are shown in Table 19 below. FIGS. 142A, 142B,and 142C show the corresponding high stress locations for the implantcomponents, which was the same for all three models tested. These datacan be used in the design of patient-specific implant components, forexample, to identify a minimum component thickness for areas of highstress. As shown in the table, there was a 24% reduction in stress with6 cuts compared to five cuts 221 MPa versus 292 MPa, interference plusno load).

TABLE 19 Inter. + No Inter. + Inter. + No Inter. + No Inter. +Interference Load Load Interference Load Load Interference Inter. + LoadLoad Perp-6-Cuts Perp-5-Cuts Flexed-6-Cuts Max Principal 246.0 221.098.1 241.3 292.0 120.5 261.4 214.0 83.5 Stress MPa Deflections (mm)Deflections (mm) Deflections (mm) Lateral Condyle 0.11 0.11 0  0.10 0.100 0.11  0.1 0 Medial Condyle 0.08 0.08 0  0.07 0.08 0 0.07  0.07 0Anterior Shield 0.18 0.19 0.05  0.17 0.18 0.06 0.20  0.21 0.05

Example 11 Tibial Implant Design and Bone Cuts

This example illustrates tibial implant components and related designs.This example also describes methods and devices for performing a seriesof tibial bone cuts to prepare a patient's tibia for receiving a tibialimplant component. Patient data, such scans of the patient's joint, canbe used to locate the point and features used to identify planes, axesand slopes associated with the patient's joint. As shown in FIG. 143A,the tibial proximal cut can be selected and/or designed to be a certaindistance below a particular location on the patient's tibial plateau.For example, the tibial proximal cut height can be selected and/ordesigned to be 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, or 4 mm or morebelow the lowest point on the patient's tibial plateau or below thelowest point on the patient's medial tibial plateau or below the lowestpoint on the patient's lateral tibial plateau. In this example, thetibial proximal cut height was selected and designed to be 2 mm belowthe lowest point on the patient's medial tibial plateau. For example, asshown in FIG. 143B, anatomic sketches (e.g., using a CAD program tomanipulate a model of the patient's biological structure) can beoverlaid with the patient's tibial plateau. As shown in FIG. 143C, thesesketched overlays can be used to identify the centers of tubercles andthe centers of one or both of the lateral and medial plateaus. Inaddition, as shown in FIGS. 144A to 144C, one or more axes such as thepatient's anatomic tibial axis 14420, posterior condylar axis 14430,and/or sagittal axis 14440 can be derived from anatomic sketches, e.g.,based on a defined a midpoint line 14450 between the patient's lateralcondyle center and medial condyle center. For example, M-L and AP planescan be determined as described in Example 9 above.

As shown in FIG. 145A, the proximal tibial resection was made a 2 mmbelow the lowest point of the patient's medial tibial plateau with a anA-P slope cut that matched the A-P slope on the patient's medial tibialplateau. As shown in FIGS. 145B and 145C, an implant profile 14500 wasselected and/or designed to have 90% coverage of the patient's cuttibial surface. In certain embodiments, the tibial implant profile canbe selected and/or designed such that tibial implant is supportedentirely or substantially by cortical bone and/or such that implantcoverage of the cut tibial surface exceeds 100% and/or has no support oncortical bone.

FIGS. 146A to 156C describe exemplary steps for performing resectioncuts to the tibia using the anatomical references identified above. Forexample, as shown in FIGS. 146A and 146B, one step can include aligningthe top of the tibial jig stylus to the top of the patient's medial andlateral spines (see arrow). As shown in FIGS. 147A and 147B, a secondstep can include drilling and pinning the tibial axis (see arrow). Asshown in FIG. 148, a third step can include drilling and pinning themedial pin (see arrow). As shown in FIG. 149, a fourth step can includeremoving the stylus. As shown in FIG. 150, a fifth step can includesawing 2 mm of tibial bone from the patient's tibial plateau with thepatient's medial AP slope. As shown in FIG. 151, a sixth step caninclude removing the resected portion of the patient's tibial plateau.As shown in FIG. 152, a seventh step can include assembling stem andkeel guide(s) onto the tibial cut guide. As shown in FIG. 153, an eighthstep can include drilling, e.g., using a 14 mm drill bit (13 mm×40 mmstem) to drill a central hole into the proximal tibial surface. As shownin FIG. 154, a ninth step can include using a saw or osteotome to createa keel slot, for example, a 3.5 mm wide keel slot. FIG. 155 shows thefinished tibial plateau with guide tools still in place. FIGS. 156A-156Cshow each of a guide tool (FIG. 156A), a tibial implant component (FIG.156B), and tibial and femoral implant components (FIG. 156C) in thealigned position in the knee.

This example shows that using a patient's joint axes (e.g., asidentified from patient-specific data and optionally from a model of thepatient's joint) to select and/or design resection cuts, e.g., thetibia, and corresponding guide tools can create resection cutsperpendicular to the patient's tibial axis and based on the patient'smedial AP slope. In addition, one or more features of the correspondingimplant components (e.g., tibial tray implant thickness) can be selectedand/or designed to align the tibial axis with the femoral axis andthereby correct the patient's alignment.

Example 12 Tibial Tray and Insert Designs

This example illustrates exemplary designs and implant components fortibial trays and inserts for certain embodiments described herein. Inparticular, this example describes a standard blank tibial tray andinsert and a method for altering the standard blanks based onpatient-specific data to include a patient-adapted feature (e.g., apatient-adapted tray and insert perimeter that substantially match theperimeter of the patient's resected tibia).

FIGS. 157A to 157E illustrate various aspects of an embodiment of astandard blank tibial implant component, including a bottom view (FIG.157A) of a standard blank tibial tray, a top view (FIG. 157B) of thestandard blank tibial tray, a bottom view (FIG. 157C) of a standardblank tibial insert, a top-front (i.e., proximal-anterior) perspectiveview (FIG. 157D) of the standard blank tibial tray, and a bottom front(i.e., distal anterior) perspective view (FIG. 157E) of apatient-adapted tibial insert. In this example and in certainembodiments, the top surface of the tibial tray can receive a one-piecetibial insert or two-piece tibial inserts. The tibial inserts caninclude one or more patient-adapted features (e.g., patient-matched orpatient-engineered perimeter profile, thickness, and/or joint-facingsurface) and/or one or more standard features, in addition to a standardlocking mechanism to engage the tibial tray. With reference to FIGS.157D and 157E, in certain embodiments the locking mechanism on the trayand insert can include, for example, one or more of: (1) a posteriorinterlock, (2) a central dovetail interlock, (3) an anterior snap, (4)an anterior interlock, and (5) an anterior wedge.

Standard blank tibial trays and/or inserts can be prepared in multiplesizes, e.g., having various AP dimensions, ML dimensions, and/or stemand keel dimensions and configurations. For example, in certain-sizedembodiments, the stem can be 13 mm in diameter and 40 mm long and thekeel can be 3.5 mm wide, 15 degrees biased on the lateral side and 5degrees biased on the medial side. However, in other-sized embodiments(e.g., having larger or small tray ML and/or AP dimensions, the step andkeel can be larger, smaller, or have a different configuration.

As mentioned above, in this example and in certain embodiments, thetibial tray can receive a one-piece tibial insert or two-piece tibialinserts. FIGS. 158A to 158C show aspects of an embodiment of a tibialimplant component that includes a tibial tray and a one-piece insert.FIGS. 159A to 159C show aspects of an embodiment of a tibial implantcomponent that includes a tibial tray and a one-piece insert.Alternatively, a two-piece tibial insert can be used with a two-piecetibial tray. Alternatively, a one-piece tibial insert can be used with atwo-piece tibial tray.

FIGS. 160A to 160C show exemplary steps for altering a blank tibial trayand a blank tibial insert to each include a patient-adapted profile, forexample, to substantially match the profile of the patient's resectedtibial surface. In particular, as shown in FIG. 160A, standard casttibial tray blanks and standard machined insert blanks (e.g., havingstandard locking mechanisms) can be finished, e.g., using CAM machiningtechnology, to alter the blanks to include one or more patient-adaptedfeatures. For example, as shown in FIG. 160B, the blank tray and insertcan be finish machined to match or optimize one or more patient-specificfeatures based on patient-specific data. The patient-adapted featuresmachined into the blanks can include for example, a patient-specificperimeter profile and/or one or more medial coronal, medial sagittal,lateral coronal, lateral sagittal bone-facing insert curvatures. FIG.160C illustrates a finished tibial implant component that includes apatient-specific perimeter profile and/or one or more patient-adaptedbone-facing insert curvatures.

Example 13 Tibial Implant Component Design

This example illustrates tibial implant component selection and/ordesign to address tibial rotation. FIGS. 161A to 161B describe exemplarytechniques for determining tibial rotation for a patient and FIG. 161Cshows resulting alignment data for the second technique.

Various tibial implant component features can optimized to ensure propertibial rotation. For example, FIG. 162 illustrates exemplary stem designoptions for a tibial tray including using stem and keel dimensions thatincrease or decrease depending on the size of the tibial implantcomponent (e.g., in the ML and/or AP dimension). Moreover, cementpockets can be employed to enhance stabilization upon implantation, Inaddition, patient-specific stem and keel guide tools can be selectedand/or designed so that the prepared stem and keel holes in a patient'sproximal tibia are properly sized, which can minimize rotation (e.g., ofa keel in a keel hole that is too large).

Another tibial implant component that can be used to address tibialrotation is selecting and/or designing a tibial tray perimeter profileand/or a tibial insert perimeter profile that minimizes overhang fromthe patient's bone (which may catch and cause rotation) and, optionally,that maximizes seating of the implant component on cortical bone.Accordingly, in certain embodiments, the tibial tray perimeter profileand/or a tibial insert perimeter profile is preoperatively selectedand/or designed to substantially match the perimeter profile of thepatient's resected tibial surface. FIGS. 163A and 163B show an approachfor identifying the patient's tibial implant perimeter profile based onthe depth and angle of the proximal tibial resection, which can appliedin the selection and/or design of the tibial tray perimeter profileand/or the tibial insert perimeter profile. As shown in the bottomimage, the lines inside the perimeter of the cut surface represent theperimeters of the various cuts in the top image taken at various depthsfrom the patient's tibial surface. FIGS. 164A and 164B show the sameapproach as described for FIGS. 163A and 163B, but applied to adifferent patient having a smaller tibia (e.g., smaller diameter andperimeter length).

Similarly, FIGS. 165A to 165D show four different exemplary tibialimplant profiles, for example, having different medial and lateralcondyle perimeter shapes that generally match various different relativemedial and lateral condyle perimeter dimensions. In certain embodiments,a tibial tray and/or insert can be selected (e.g., preoperatively orintraoperatively) from a collection or library of implants for aparticular patient (i.e., to best-match the perimeter of the patient'scut tibial surface) and implanted without further alteration to theperimeter profile. However, in certain embodiments, these differenttibial tray and/or insert perimeter profiles can serve as blanks. Forexample, one of these tibial tray and/or insert profiles can be selectedpreoperatively from a library (e.g., an actual or virtual library) for aparticular patient to best-match the perimeter of the patient's cuttibial surface. Then, the selected implant perimeter can be designed orfurther altered based on patient-specific data, for example, tosubstantially match the perimeter of the patient's cut tibial surface.

As described in this example, various features of a tibial implantcomponent can be designed or altered based on patient-specific data. Forexample, the tibial implant component design or alterations can be madeto maximize coverage and extend to cortical margins; maximize medialcompartment coverage; minimize overhang from the medial compartment;avoid internal rotation of tibial components to avoid patellardislocation; and avoid excessive external rotation to avoid overhanglaterally and impingement on the popliteus tendon.

Example 14 Bone Cuts Using a Femur-First Jig Set

This example describes methods and devices for performing a series ofbone cuts to receive a patient-specific implant. Specifically, a set ofjigs is designed in connection with the design of a patient-specificimplant component. The designed jigs guide the surgeon in performing oneor more patient-specific cuts to the bone so that those cut bonesurface(s) negatively-match the patient-specific bone cuts of theimplant component. The set of jigs described in this example aredesigned for a femur-first cut technique.

In a first step, shown in FIGS. 166A and 166B, a first femur jig is usedto establish peg holes and pin placements for a subsequent jig used fora distal cut. In this example, the first jig is designed to circumvent 3mm of cartilage thickness. In a second step, shown in FIGS. 167A and167B, the distal cut is performed with a second femur jig. In thisexample, the second jig is patient-specific. However, in certainembodiments that apply a traditional distal cut, a standard jig can beused. In a third step, as shown in FIG. 168A, the anterior cut, theposterior cut, and the chamfer cuts are performed with a third femurjig. In this example, the jig includes slots that are 1.5 mm wide toallow for a saw blade thickness (i.e., no metal guides). As shown inFIG. 168B, in certain embodiments, for implant component designs havingsix or more inner, bone-facing surfaces, for example, having one or twoadditional chamfer cuts, the additional cuts can be performed using oneor more additional jigs. In this example, the additional jig is designedto accommodate two steep additional chamfer cuts.

Next, the tibia is cut using one or more jigs designed to makepatient-specific cuts to the tibia. An exemplary tibial jig is depictedin FIGS. 169A and 169B. A tibial alignment pin 16900 is used to helpproperly orient the jig. The portion 16910 of the jig inserted betweenthe femur and tibia can have a variable thickness. In certainembodiments, the tibial jig can be designed to accommodate for compositethickness from the distal cut femur 16920. Alternatively oradditionally, a balancing chip can be used to address differences in thedistance between the tibia and femur surfaces. For example, in certainembodiments a tibia jig may be designed to rest on 2 mm of cartilage,while a balancing chip is designed to rest on the distal cut femur.

A balancing chip is shown in FIG. 170. If a varus deformity of the kneeis observed, virtual realignment can be addressed by including addedthickness to the balancing chip in the area that would produce a leg inneutral alignment 17010. For a grossly mal-aligned contra-lateral leg,correction can be per a surgeon's order. The balancing chip can includea feature 17020 to attach it to the tibia jig, and thereby allow foraccurate distal placement of the tibial cut while at the same timeaccommodating for composite thickness. An exemplary balancing chipattached to a tibia jig is shown in FIGS. 171A and 171B. To facilitateattachment, the balancing chip handle 18000 matches the tibial slopedesigned into the tibial cut and tibial implant. Preferably, thebalancing chip is designed to enter into the joint easily.

Example 15 Bone Cuts Using a Tibial-First Jig Set

This example describes methods and devices for performing a series ofbone cuts to receive a patient-specific implant. Specifically, a set ofjigs is designed in connection with the design of a patient-specificimplant component. The designed jigs guide the surgeon in performing oneor more patient-specific cuts to the bone so that those cut bonesurface(s) negatively-match the patient-specific bone cuts of theimplant component. The set of jigs described in this example aredesigned for cuts to a femoral implant component in a tibia-first cuttechnique.

In a first step, shown in FIG. 172, a first jig is used to establishplacement and alignment of femoral implant peg holes. In the example,the placement is flexed 5 degrees with respect to the sagittal femoralaxis. In a second step, shown in FIG. 173, a second jig is used toestablish placement pins for the distal cut jig. The second jig can havedifferent thicknesses 17300 to accommodate composite thickness from thecut tibial surface. In a third step, as shown in FIG. 174, a distal cutjig is positioned based on the placement established by the previousjig. The distal cut jig can be patient-specific or standard. Lastly, asshown in FIG. 175, remaining cuts are performed with a chamfer cut jig.In the example, the anterior cut is not oblique.

INCORPORATION BY REFERENCE

The entire disclosure of each of the publications, patent documents, andother references referred to herein is incorporated herein by referencein its entirety for all purposes to the same extent as if eachindividual source were individually denoted as being incorporated byreference.

EQUIVALENTS

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The foregoingembodiments are therefore to be considered in all respects illustrativerather than limiting on the invention described herein. Scope of theinvention is thus indicated by the appended claims rather than by theforegoing description, and all changes that come within the meaning andrange of equivalency of the claims are intended to be embraced therein.

We claim:
 1. A knee replacement system for implantation in a knee jointof a patient, comprising: a knee replacement implant including a femoralimplant for implantation on a femur of the patient and a tibial implantfor implantation on a tibia of the patient, the femoral implantincluding a lateral condyle portion having a curved condylar shape in asagittal plane and having a lateral weight bearing surface configured toarticulate with the tibial implant when the tibial and femoral implantsare implanted in the knee joint of the patient and an inner surfaceconfigured to abut one or more bone cut surfaces of a femur when thefemoral implant is implanted in the knee joint of the patient, whereinthe lateral condyle portion has a narrowed posterior portion, such thata width of the lateral condyle portion measured in substantially amediolateral direction narrows in the lateral posterior portion relativeto a distal part of the lateral condylar portion, and the tibial implantincluding a lateral weight bearing surface configured to articulate withthe lateral weight bearing surface of the femoral implant along anarticulating region in a generally sagittal direction when the tibialand femoral implants are implanted in the knee joint of the patient, anda bone-facing surface configured to abut a surface of a tibia of thepatient when the tibial implant is implanted in the knee joint of thepatient, wherein the tibial lateral weight bearing surface includes avariable slope having a at least one portion forming a negative sloperelative to the bone facing surface in an anteroposterior direction andat least one portion forming a positive slope relative to the bonefacing surface anteroposterior direction.
 2. The knee implant system ofclaim 1 wherein the variable slope of the tibial lateral weight bearingsurface forms a convex weight bearing surface portion substantially inan anteroposterior direction.
 3. The knee implant system of claim 1,wherein the variable slope of the tibial lateral weight bearing surfaceforms a convex weight bearing surface portion substantially in ananteroposterior direction and a concave weight bearing surface portionsubstantially in an anteroposterior direction.
 4. The knee implantsystem of claim 1, wherein the variable slope of the tibial lateralweight bearing surface forms a convex weight bearing surface portionsubstantially in an anteroposterior direction and a concave weightbearing surface portion substantially in an anteroposterior directionthat is positioned posteriorly relative to the convex weight bearingsurface portion.
 5. The knee implant system of claim 1, wherein thevariable slope of the tibial lateral weight bearing surface forms aconvex weight bearing surface portion substantially in ananteroposterior direction and a concave weight bearing surface portionsubstantially in an anteroposterior direction that is positionedanteriorly relative to the convex weight bearing surface portion.
 6. Theknee implant system of claim 1, wherein the variable slope of the tibiallateral weight bearing surface forms a convex weight bearing surfaceportion substantially in an anteroposterior direction, a first concaveweight bearing surface portion substantially in an anteroposteriordirection that is positioned anteriorly relative to the convex weightbearing surface portion, and a second concave weight bearing surfaceportion substantially in an anteroposterior direction that is positionedposteriorly relative to the convex weight bearing surface portion. 7.The knee implant system of claim 1, wherein the narrowed posteriorportion is configured to avoid soft tissue impingement.
 8. The kneeimplant system of claim 7, wherein the tibial implant and femoralimplant are configured to avoid impingement of the femoral implant onthe popliteus tendon of the patient by the femoral implant when thetibial implant is implanted in the patient and the femoral implant is ina flexed position relative to the tibial implant.
 9. The knee implantsystem of claim 1, wherein the tibial lateral weight bearing surface iscurved in a mediolateral direction.
 10. The knee implant system of claim1, wherein the tibial lateral weight bearing surface is concavesubstantially in a coronal plane.
 11. The knee implant system of claim1, wherein the tibial lateral weight bearing surface is convexsubstantially in a coronal plane.
 12. A knee replacement system forimplantation in a knee joint of a patient, comprising: a kneereplacement implant including a femoral implant for implantation on afemur of the patient and a tibial implant for implantation on a tibia ofthe patient, the femoral implant including a lateral condyle portionhaving a generally curved lateral condylar shape, and having a lateralweight bearing surface configured to articulate with the tibial implantwhen the tibial and femoral implants are implanted in the knee joint ofthe patient and an inner surface configured to abut one or more bone cutsurfaces of a lateral condyle of a femur when the femoral implant isimplanted in the knee joint of the patient, wherein the lateral condyleportion includes a lateral distal portion and a lateral posteriorportion; and the femoral implant further including a medial condyleportion having a generally curved medial condylar shape and having amedial bearing surface configured to articulate with the tibial implantwhen the tibial and femoral implants are implanted in the knee joint ofthe patient and a second inner surface configured to abut one or morebone cut surfaces of a medial condyle of the femur when the femoralimplant is implanted in the knee joint of the patient, wherein themedial condyle portion includes a medial distal portion and a medialposterior portion, wherein the medial distal portion of the medialcondyle portion and the lateral distal portion of the lateral condyleportion each having substantially the same width measured insubstantially the mediolateral direction and the medial posteriorportion of the medial condyle portion being wider than the lateralposterior portion of the lateral condyle portion measured insubstantially the mediolateral direction; and further comprising atibial implant including a lateral plateau portion with a lateralplateau bearing surface configured to articulate with the lateral weightbearing surface of the femoral implant when the tibial and femoralimplants are implanted in the knee joint of the patient, a medialplateau portion with a medial plateau bearing surface configured toarticulate with the medial bearing surface of the femoral implant whenthe tibial and femoral implants are implanted in the knee joint of thepatient, and a bone-facing surface configured to abut a cut proximal endof a tibia of the patient when the tibial implant is implanted in theknee joint of the patient, wherein the lateral plateau bearing surfaceincludes a variable slope having a at least one portion forming anegative slope relative to the bone facing surface and at least oneportion forming a positive slope relative to the bone facing surface.13. The knee replacement system of claim 12, wherein the medial plateaubearing surface is configured to be offset in a distal directionrelative to the lateral plateau bearing surface when the tibial implantis implanted in the patient.
 14. The knee replacement system of claim12, wherein the lateral distal portion of the lateral condyle portion iswider than the lateral posterior portion of the lateral condyle portionmeasured in substantially the mediolateral direction.
 15. The kneereplacement system of claim 12, wherein the variable slope of thelateral plateau bearing surface forms a convex weight bearing surfaceportion substantially in an anteroposterior direction.
 16. The kneereplacement system of claim 12, wherein the variable slope of thelateral plateau bearing surface forms a convex weight bearing surfaceportion substantially in an anteroposterior direction and a concaveweight bearing surface portion substantially in an anteroposteriordirection.
 17. The knee replacement system of claim 12, wherein thevariable slope of the lateral plateau bearing surface forms a convexweight bearing surface portion substantially in an anteroposteriordirection and a concave weight bearing surface portion substantially inan anteroposterior direction that is positioned posteriorly relative tothe convex weight bearing surface portion.
 18. The knee replacementsystem of claim 12, wherein the variable slope of the lateral plateaubearing surface forms a convex weight bearing surface portionsubstantially in an anteroposterior direction, a first concave weightbearing surface portion substantially in an anteroposterior directionthat is positioned anteriorly relative to the convex weight bearingsurface portion, and a second concave weight bearing surface portionsubstantially in an anteroposterior direction that is positionedposteriorly relative to the convex weight bearing surface portion. 19.The knee replacement system of claim 12, wherein the lateral condyleportion has a narrowed posterior portion, such that the width of thelateral condyle portion measured in substantially the mediolateraldirection narrows in a posterior part of the lateral condylar portion.20. The knee replacement system of claim 19, wherein the tibial implantand femoral implant are configured to avoid impingement of the femoralimplant on the popliteus tendon of the patient by the femoral implantwhen the tibial implant is implanted in the patient and the femoralimplant is in a flexed position relative to the tibial implant.
 21. Theknee replacement system of claim 12, wherein the medial posteriorportion is wider than the lateral posterior portion when measured insubstantially the mediolateral direction and the posterior medialportion is thicker than the lateral posterior portion.
 22. The kneereplacement system of claim 12, wherein the lateral posterior portionincludes a bone cut facet on the inner surface, and the medial posteriorportion includes a bone cut facet on the second inner surface, andwherein the bone facet cuts are not coplanar.
 23. The knee replacementsystem of claim 12, wherein the inner surface of the lateral posteriorportion includes a lateral facet surface and the second inner surface ofthe medial posterior portion includes a corresponding medial facetsurface, each of the lateral facet surface and the medial facet surfacebeing substantially planar, and wherein the lateral facet surface isoriented in a different plane from the medial facet surface.
 24. Theknee replacement system of claim 12, wherein the lateral plateau bearingsurface is curved in a mediolateral direction.
 25. The knee replacementsystem of claim 12, wherein the lateral plateau bearing surface isconcave substantially in a coronal plane.
 26. The knee replacementsystem of claim 12, wherein the lateral plateau bearing surface isconvex substantially in a coronal plane.
 27. A knee implant system forimplantation in a knee joint of a patient, comprising: a femoral implanthaving a medial condyle portion and a lateral condyle portion, whereinthe lateral condyle portion includes a lateral periphery configured toaccommodate a popliteus tendon of the knee joint of the patient; atibial implant configured for implantation in a lateral compartment of aknee and having a weight bearing surface configured to articulate withan opposing articular surface in a generally sagittal direction when thetibial and femoral implants are implanted in the knee joint of thepatient, and a bone-facing surface configured to abut a surface of atibia of the patient when the tibial implant is implanted in the kneejoint of the patient, wherein the weight bearing surface includes avariable slope having at least one portion forming a negative sloperelative to the bone facing surface in an anteroposterior direction andat least one portion forming a positive slope relative to the bonefacing surface anteroposterior direction, and wherein the weight bearingsurface includes a convex portion in a mediolateral direction.
 28. Aknee replacement system for implantation in a knee joint of a patient,comprising: a knee replacement implant including a femoral implant forimplantation on a femur of the patient and a tibial implant forimplantation on a tibia of the patient, the femoral implant including alateral condyle portion having a generally curved lateral condylarshape, and having a lateral weight bearing surface configured toarticulate with the tibial implant when the tibial and femoral implantsare implanted in the knee joint of the patient and an inner surfaceconfigured to abut one or more bone cut surfaces of a lateral condyle ofa femur when the femoral implant is implanted in the knee joint of thepatient, wherein the lateral condyle portion includes a lateral distalportion and a lateral posterior portion; and the femoral implant furtherincluding a medial condyle portion having a generally curved medialcondylar shape and having a medial bearing surface configured toarticulate with the tibial implant when the tibial and femoral implantsare implanted in the knee joint of the patient and a second innersurface configured to abut one or more bone cut surfaces of a medialcondyle of the femur when the femoral implant is implanted in the kneejoint of the patient, wherein the medial condyle portion includes amedial distal portion and a medial posterior portion; wherein the medialdistal portion of the medial condyle portion and the lateral distalportion of the lateral condyle portion each have substantially the samewidth measured in substantially the mediolateral direction and themedial posterior portion of the medial condyle portion is wider than thelateral posterior portion of the lateral condyle portion measured insubstantially the mediolateral direction; and further comprising atibial implant including a lateral plateau portion with a lateralplateau bearing surface configured to articulate with the lateral weightbearing surface of the femoral implant when the tibial and femoralimplants are implanted in the knee joint of the patient, a medialplateau portion with a medial plateau bearing surface configured toarticulate with the medial bearing surface of the femoral implant whenthe tibial and femoral implants are implanted in the knee joint of thepatient, and a bone-facing surface configured to abut a cut proximal endof a tibia of the patient when the tibial implant is implanted in theknee joint of the patient, wherein the lateral plateau bearing surfaceincludes a variable slope having at least one portion forming a negativeslope in a sagittal direction and relative to the bone facing surfaceand at least one portion forming a positive slope in a sagittaldirection and relative to the bone facing surface.
 29. The kneereplacement system of claim 28, wherein the positive slope and thenegative slope form a generally convex curve in a sagittal direction.30. The knee replacement system of claim 28, wherein the positive slopeand the negative slope form a generally convex curve in a coronaldirection.